Insights10 min read
Can You Model Build-to-Rent in ARGUS? A UK Guide to BTR Cash Flows
Short answer: Yes. ARGUS build-to-rent modelling is possible: ARGUS Enterprise, the cash flow and valuation software made by Altus Group, supports multifamily leases. The harder question is fit. A build-to-rent (BTR) scheme has hundreds of short tenancies. Its cash flow depends on empty flats, resident turnover, rent collection and running costs, which practitioner evidence suggests owners often model in spreadsheets.
By Sooraj Rup, Founder, Edoras Asset Management. Published 21 October 2026.
Can ARGUS Enterprise model a build-to-rent scheme?
Yes, ARGUS Enterprise can model a build-to-rent scheme. As of October 2026, Altus lists multifamily leases (the US term for blocks of rental flats) alongside office, industrial and retail leases on its product page.
Altus describes ARGUS Enterprise as industry-standard software for commercial property valuation and cash flow forecasting. It supports UK valuation methods such as term and reversion, which value current and expected future rent separately. Lenders and valuers know its outputs, which is a real advantage.
ARGUS Developer is also widely used in UK development viability work. A review prepared for the London Borough of Camden in January 2025, for example, contains a student housing appraisal run in ARGUS Developer. Altus also lists build-to-rent as a project type in ARGUS EstateMaster.
Altus is also modernising. As of October 2026, ARGUS Enterprise sits inside the cloud-based ARGUS Intelligence Platform. Altus unveiled ARGUS Assist, an AI layer within its ARGUS Intelligence Platform, on 14 April 2026. Altus's product roadmap lists bringing in and checking rent schedules (rent rolls) and operating costs automatically as planned work.
So the real question is whether a tool built around commercial leases and periodic models suits an asset whose value depends on daily operations. In our view, that is where the fit gets weaker.
How is a BTR cash flow different from an office cash flow?
A BTR cash flow is driven by hundreds of short tenancies and by how well the building is run. An office cash flow is driven by a few long leases.
In a multi-let office, the model tracks each lease. That means the rent, review dates, early exit rights, expiry and which costs the tenant pays back. Lease-by-lease software is designed for that.
A 150-unit BTR block looks quite different:
- Many short tenancies. Many residents stay for a year or two. Every month, some leave and some arrive.
- Void days. Each move-out leaves a flat empty while it is cleaned, repaired and re-let. A few extra days, across dozens of move-outs a year, add up.
- Churn. The share of residents who leave each year. Higher churn means more void days and more re-letting cost.
- Gross-to-net. BTR owners pay most running costs themselves: staff, utilities, repairs, insurance, marketing, letting fees and amenities. Practitioners often express the gap between gross rent and net income as a "gross-to-net" percentage. A September 2018 JLL study of seven stabilised UK schemes found an average gross-to-net of 26.6%, with a range of 21.3% to 35%. The data is dated and the sample small, so treat it as a rough guide only.
- Rent collection. Some rent is paid late or not at all. Arrears and bad debt need their own line.
The Renters' Rights Act. In England, the main reforms under the Renters' Rights Act 2025 took effect on 1 May 2026, as the government's implementation roadmap sets out. Most fixed-term tenancies are replaced by rolling (periodic) tenancies. Tenants can leave with two months' notice. Section 21 "no fault" evictions are abolished. Rents can rise only once a year, with two months' notice. This is not legal advice. Tenancy length, churn, rent increase timing and arrears recovery may now differ from pre-2026 history, so those assumptions deserve fresh thought.
None of this is impossible in ARGUS. But these drivers change monthly and come from operations rather than lease documents.
What inputs does a UK BTR model need?
A UK build-to-rent financial model needs a unit mix, rents, occupancy, churn, an operating cost budget, and views on rent growth and collection. That holds for underwriting and for running the asset.
| Input | What it means | Where it usually comes from |
|---|---|---|
| Unit mix | Number of studios, one-, two- and three-bed flats, and their sizes | Development plans, as-built schedule |
| Asking rent per unit type | Monthly rent for each unit type | Lettings data, local comparables, valuer advice |
| Achieved rent | Rent actually agreed, after any incentives such as rent-free weeks | Property management system (the software that holds tenancies and payments) |
| Stabilised occupancy | The share of units let once the scheme has finished its first letting period and settled down | Operating history, comparable schemes |
| Lease-up period | Months taken to let a new scheme for the first time | Lettings agent, comparables |
| Churn | Share of residents leaving each year | Operating history |
| Void days per move-out | Days a flat sits empty between residents | Operating history, maintenance logs |
| Re-letting cost per move-out | Cleaning, repairs, tenant checks (referencing), marketing | Maintenance and lettings invoices |
| Bad debt and arrears | Share of rent not collected | Rent ledger |
| Operating costs | Staff, utilities, repairs, insurance, amenities, management fees | Budget, actual costs from the operator |
| Rent growth | Expected annual change in rents | Market data, valuer advice, tenancy law limits |
| Capital expenditure | Replacement of kitchens, flooring, lifts, boilers and other building equipment over time | Long-term replacement cost plan |
Most of these inputs come from the building's day-to-day operations, as the right-hand column shows.
What do most UK BTR owners use today?
Practitioner evidence suggests much UK BTR operating modelling is done in spreadsheets, often alongside an ARGUS file for valuation or lending. We found no UK survey measuring it, so treat this as a pointer only.
"Currently, most build-to-rent developers are working in Excel," said Altus Group, writing in 2021 about build-to-rent feasibility in Australia. That was a different market five years ago, and the article was promoting Altus's own EstateMaster tool for BTR feasibility.
A.CRE, a practitioner resource, describes Excel as the industry-standard tool. It sees ARGUS's main edge in handling complex commercial service charge recoveries (reimbursements), which matter less in residential. In a 2014 US forum thread on ARGUS for multifamily, some practitioners saw little benefit. Others said some funds, investors or lenders preferred or required ARGUS-format output.
In short, ARGUS is common for valuation, lending and development appraisal. Day-to-day operating models appear more often to be spreadsheets. Valuers follow the RICS professional standard on valuing residential property purpose built for renting and choose their own tools.
Spreadsheets are flexible and familiar. So are their limits: manual updates, version control and reconciling with the property management system. For more, see why owners use ARGUS instead of Excel.
How can a model stay in line with live operating data?
A model stays in line with operations when it is fed directly from the building's own records, rather than rebuilt by hand each quarter. Those records include the rent ledger, tenancy data and actual costs.
In many traditional set-ups, someone exports data from the property management system, cleans it and pastes it into a spreadsheet or ARGUS file, often quarterly. Between updates, model and building can drift apart.
An AI-native workflow can work differently. In general terms, describing no specific system:
- Unit-level data (tenancies, rents, move-outs, arrears, repairs, costs) is pulled from operating systems on a regular schedule.
- Software checks the data for gaps and errors and flags anything unusual, such as a rise in void days on one floor.
- The forecast is designed to be updated as new operating data arrives, so a change in churn or collection shows up in the cash flow quickly.
- An asset manager reviews the changes, decides what they mean and signs off. People make the judgement calls, and the technology carries the repetitive work.
Edoras Asset Management, a London-based, early-stage asset manager for UK build-to-rent, student housing, senior housing and hotels, is being built around that split. Edoras is launching its first tool, for leasing administration, in October 2026. The rest of the workflow described here is in development.
Lenders and valuers often still want outputs in familiar formats, including ARGUS. Any manager, whatever its tools, needs to be able to provide those.
Illustrative example: how do void days affect income in a 150-unit BTR scheme?
In this illustrative example, 14 extra void days per move-out cut net operating income by about £50,000 a year. The numbers are simple assumptions, not real scheme data or Edoras results.
Assumptions:
- 150 flats let at an average of £1,825 per month, or £60 per flat per day (£1,825 x 12 / 365).
- Churn of 40% a year, so 60 move-outs a year (150 x 40%).
- Bad debt of 1% of rent due.
- Operating costs of £5,500 per flat per year, so £825,000 in total.
- Re-letting cost of £500 per move-out, so £30,000 a year (60 x £500).
- We compare two cases: 21 void days per move-out, and 35 void days per move-out.
How void days flow to income:
| Line | 21 void days | 35 void days |
|---|---|---|
| Gross rent if fully let (150 x £1,825 x 12) | £3,285,000 | £3,285,000 |
| Total void days (60 x void days) | 1,260 | 2,100 |
| Rent lost to voids (void days x £60) | £75,600 | £126,000 |
| Average occupancy | 97.7% | 96.2% |
| Rent due after voids | £3,209,400 | £3,159,000 |
| Bad debt (1%) | £32,094 | £31,590 |
| Rent collected | £3,177,306 | £3,127,410 |
| Operating costs | £825,000 | £825,000 |
| Re-letting costs | £30,000 | £30,000 |
| Net operating income | £2,322,306 | £2,272,410 |
| Operating and re-letting costs as a share of rent collected | 26.9% | 27.3% |
| Gross-to-net (gross rent less net operating income, as a share of gross rent) | 29.3% | 30.8% |
Net operating income means rent collected less the costs of running the building, before financing and tax.
What it shows. Fourteen extra void days per move-out cost £50,400 in lost rent (840 extra void days x £60). Bad debt falls slightly, by £504, because less rent is due. The net effect is £49,896 less net operating income a year, about 2% lower.
The example shows two things. First, occupancy only moves from 97.7% to 96.2%, so a healthy headline can hide slower turnarounds. Second, void days depend on repair speed and re-letting planning. A model that sees occupancy once a quarter will notice late.
A real model would also cover lease-up, rent growth, capital spending and incentives.
FAQ
Can ARGUS be used for build-to-rent?
Yes. As of October 2026, ARGUS Enterprise supports multifamily leases, and ARGUS Developer is widely used in UK development viability appraisals. Many owners use ARGUS for valuation and lending, and spreadsheets for the operating model. The question is less about capability and more about which tool fits the day-to-day work of running the asset.
Is ARGUS or Excel better for a BTR financial model?
Each has strengths. ARGUS is standardised and familiar to lenders and valuers. Spreadsheets handle unit-level operating detail easily, but are usually updated by hand and harder to audit. Many UK owners use both. The bigger question is how the model is kept in line with what is happening in the building.
What is a typical gross-to-net for UK BTR?
A 2018 JLL study of seven stabilised schemes found an average gross-to-net of 26.6%, with a range of 21.3% to 35%. That data is dated. Rising staff, energy, insurance and compliance costs may have moved it, so use current operator budgets and actual costs where you can.
What are void days in a BTR model?
Void days are the days a flat sits empty between one resident leaving and the next moving in, covering cleaning, repairs, marketing and tenant checks. Total void days equal move-outs multiplied by void days per move-out. Small changes in turnaround time can therefore have a noticeable effect on income across a large scheme.
How does the Renters' Rights Act affect BTR modelling?
In England, the main reforms took effect on 1 May 2026. Most tenancies become rolling, tenants can leave with two months' notice, section 21 evictions end, and rents can rise only once a year with two months' notice. Owners may want to revisit churn, rent increase timing and arrears assumptions. Take legal advice on the detail.
Do lenders still expect an ARGUS file for BTR?
Often, yes, particularly for valuation and debt. ARGUS output is a common language for lenders, valuers and owners. Whatever tools an owner or manager uses, it makes sense to provide outputs in the formats lenders and valuers expect. We cover this in more detail in ARGUS vs Excel vs AI-native asset management.
Learn more about our asset management for UK living sectors.
Sooraj Rup is the founder of Edoras Asset Management. He previously spent two years at an institutional real estate investment firm managing about $18 billion of assets, where he worked on roughly $800 million of transactions.
If you own or are developing a build-to-rent, student or senior housing scheme and want to talk about how it is managed, contact us.
ARGUS, ARGUS Enterprise, ARGUS Intelligence, ARGUS Assist, ARGUS Developer and ARGUS EstateMaster are trade marks of Altus Group or its affiliates, including ARGUS Software, Inc. Excel is a trade mark of Microsoft Corporation. Edoras Asset Management is not affiliated with, sponsored by or endorsed by Altus Group or Microsoft. References are for descriptive and comparative purposes only. This article is for information only and is not an offer or invitation to invest.