The problem
Buy-to-let clients are often the most commercially sophisticated clients a mortgage broker works with, and they expect a higher level of analytical support than a standard owner-occupier. An investor considering a property wants to know whether it will generate positive cash flow, how different mortgage options affect the yield, what the stress test implications are for the mortgage they can access, and how the target property compares to the wider market in the area. Providing that analysis properly takes time and requires pulling together data from multiple sources.
The lender side is particularly complex. BTL mortgage affordability is stress-tested differently from residential, and the specifics vary significantly by lender, property type, and whether the client is a basic rate or higher rate taxpayer. A property that passes the stress test with one lender may not pass with another, and the difference can have a significant effect on what deposit the client needs or which lenders are available to them. Keeping on top of current stress test requirements across the market, while also doing the yield calculations and the market research, is a substantial task.
Many brokers do some of this analysis but rarely all of it, and rarely in a form that is easy to present to the client. Investor clients who receive a clear, structured analysis with numbers they can actually use make faster decisions and are more likely to refer other investors. AI makes it practical to produce this level of analysis consistently rather than only when time allows.
The system
Step 1: Research current rental yields for the target area (Perplexity)
Use Perplexity to quickly research rental market data for the specific area and property type the client is considering. Because Perplexity pulls from live sources, it can give you more current market data than static databases.
Prompt example: "What are the current average rental yields for two-bedroom flats in [specific area or postcode district] in [city]? Please provide data on average rental prices, typical asking prices, and indicative gross yields. Also summarise any relevant trends in the local rental market, including vacancy rates, demand drivers, and any planned developments that could affect supply or demand."
Follow-up prompt: "How does [specific area] compare to other areas in [city] for BTL yield? Which areas are currently considered higher yield and what are the trade-offs in terms of property quality, tenant demand, and capital growth prospects?"
Cross-reference AI research with current data from Rightmove, Zoopla, and any local agent intelligence you have. Treat AI as a quick starting point for a conversation, not a definitive data source.
Step 2: Run the yield calculations (Claude)
Provide the property details and ask Claude to run a full yield and cash flow analysis.
Prompt example: "Please run a detailed buy-to-let yield analysis for the following scenario: Purchase price: £185,000. Estimated monthly rental income: £950. Mortgage: 75% LTV, £138,750 borrowed. Please calculate: gross yield, net yield assuming typical costs (management fee 10%, maintenance allowance 1% of property value annually, landlord insurance £200/year, void allowance 5%). Please then show the monthly cash flow and annual cash flow at three different mortgage rates: 4.5%, 5.0%, and 5.5% interest-only. Finally, show the impact on cash flow if the rent achieves 10% below the estimated figure."
This gives the investor a clear sensitivity analysis rather than just a single optimistic scenario. Serious investors find this much more useful and it demonstrates a more thorough level of analysis.
Step 3: Check lender stress test implications (Claude)
Use Claude to work through the stress test arithmetic for the lenders you are considering and explain the implications clearly.
Prompt example: "For a BTL purchase of £185,000 at 75% LTV (£138,750 mortgage), I need to understand the lender stress test requirements. The anticipated rental income is £950/month (£11,400/year). Please calculate: (1) whether this rental income passes a typical 125% stress test at a notional rate of 5.5%, (2) whether it passes a 145% stress test at 5.5% (as required for higher rate taxpayers by many lenders), and (3) what the minimum rental income required would be to pass each stress test. If the property fails the test, how much additional deposit would the client need to provide to bring the mortgage down to a level that does pass?"
This calculation is quick for Claude but takes time to do manually, and getting it wrong leads to applications that fail at underwriting.
Step 4: Produce a client briefing document (Claude)
Bring together your research and calculations into a structured investor briefing that the client can review.
Prompt example: "Please draft a structured BTL investment analysis briefing for an investor client. Include the following sections: property overview and purchase summary, rental market context for the area, gross and net yield analysis, monthly and annual cash flow at three rate scenarios, stress test position and lender implications, key risks and sensitivities, and a summary of next steps. Use clear professional language suitable for a commercially aware investor. [Paste your research and calculations]"
The results
Before: Putting together a thorough BTL analysis for an investor client took an experienced broker 60 to 90 minutes, drawing on multiple sources. Many brokers did not provide written analysis at all, presenting numbers verbally or in a brief email.
After: A full investor briefing document is produced in 25 to 35 minutes. The quality of the analysis is consistently higher, with sensitivity scenarios and stress test implications included as standard rather than as extras for favoured clients. Investor clients who receive the structured briefing convert faster, refer more frequently, and are better prepared for the mortgage conversation. One broker attributed a significant increase in BTL pipeline to providing written investment analysis as a standard part of the service, differentiating from competitors who treated BTL as "just another mortgage".