Mortgage Comparison for Buy to Let Explained

Last updated: 20 July 2026

If you are considering investing in rental property, choosing the right mortgage is one of the most important financial decisions you will make. Buy to let mortgages work differently from residential mortgages, and comparing them properly requires more than simply looking at the headline interest rate.

This guide explains mortgage comparison for buy to let, what factors actually matter, and how UK landlords can make sense of the options available.

What is a buy to let mortgage?

A buy to let mortgage is designed for properties that will be rented out rather than lived in by the owner. Because the loan is usually repaid using rental income, lenders assess these mortgages differently from residential borrowing.

Key differences include:

1. Higher minimum deposit requirements
2. Interest-only repayments are more common
3. Affordability is based mainly on rental income
4. Rates and fees vary more widely between lenders

These differences mean that buy to let mortgage comparison requires a more detailed approach.

Why mortgage comparison matters for buy to let

Buy to let mortgages are often held for years, and even small differences in rates or fees can significantly affect long-term returns.

Comparing mortgages properly helps landlords:

1. Understand the true cost of borrowing
2. Avoid unsuitable mortgage structures
3. Balance monthly cash flow with overall cost
4. Match borrowing to their investment strategy

Focusing only on the lowest advertised rate can be misleading, particularly when fees or restrictive terms are involved.

Key factors to compare in buy to let mortgages

Interest rates

Interest rates are usually the first thing landlords compare, but they should not be considered in isolation.

Buy to let rates may be:

1. Fixed for a set period, commonly two or five years
2. Variable or tracker-based
3. Higher than residential mortgage rates

When comparing rates, it is important to check how long the rate applies, what happens when it ends, and whether it is linked to any external benchmark.

Fees and upfront costs

Fees can make a significant difference to the overall cost of a buy to let mortgage.

Common costs include:

1. Arrangement or product fees
2. Valuation fees
3. Legal costs
4. Broker fees, where applicable

A mortgage with a low rate but high fees may not be cost-effective if you plan to remortgage or sell within a few years.

Loan to value (LTV)

Loan to value refers to the percentage of the property’s value you are borrowing.

Most buy to let mortgages require:

1. A deposit of at least 20% to 25%
2. Lower rates at lower LTV levels

When comparing mortgages, focus only on products available at your actual LTV, as headline rates may not apply across all borrowing levels.

Rental coverage requirements

Instead of standard income checks, buy to let lenders use rental coverage calculations.

Typically:

1. Rental income must exceed mortgage interest by a set percentage
2. Affordability is stress-tested at higher interest rates

Different lenders apply different formulas, which can affect how much you are able to borrow, even if the interest rates appear similar.

Repayment type

Most buy to let mortgages are interest-only, though repayment options are available.

Interest-only mortgages:

1. Lower monthly payments
2. Require a clear plan to repay the capital
3. Are common among experienced landlords

Repayment mortgages:

1. Gradually reduce the loan balance
2. Cost more each month
3. May suit long-term, lower-risk strategies

Mortgage comparison should always include repayment structure, not just price.

Fixed vs variable buy to let mortgages

Fixed-rate mortgages

Fixed-rate buy to let mortgages provide certainty by locking in the interest rate for a set period.

They can help with:

1. Predictable monthly costs
2. Protection from rate rises
3. Longer-term planning

However, they often come with early repayment charges if you exit the deal early.

Variable and tracker mortgages

Variable mortgages can change over time, either at the lender’s discretion or in line with the Bank of England base rate.

They may offer:

1. Greater flexibility
2. Potential savings if rates fall
3. Fewer early repayment charges in some cases

They also introduce more uncertainty, particularly in a rising rate environment.

Comparing buy to let mortgages beyond price

Flexibility and features

Some mortgages include features that may be valuable depending on your plans, such as:

1. Overpayment allowances
2. Portability to another property
3. Easier remortgaging options

These features are not always obvious in comparison tables but can matter in practice.

Portfolio vs single-property landlords

Lenders often apply stricter criteria to portfolio landlords.

If you own multiple rental properties:

1. Additional documentation may be required
2. Fewer lenders may be available
3. Mortgage comparison becomes more complex

Your experience level and portfolio size should always be factored into the comparison process.

The role of a buy to let mortgage broker

Buy to let mortgages are not always easy to compare directly, as many products are only available through intermediaries.

Working with a specialist buy to let mortgage broker can help landlords compare lenders beyond headline rates and understand how different affordability models work. Brokers can also identify suitable options based on rental income, property type, and long-term plans.

This can be particularly useful where criteria are complex or where lenders apply different stress-testing rules.

Common mistakes when comparing buy to let mortgages

Some of the most common issues include:

1. Focusing only on interest rates
2. Ignoring fees and total cost
3. Overlooking rental stress testing
4. Choosing inflexible deals without future planning
5. Assuming all lenders assess affordability the same way

Avoiding these mistakes leads to more effective mortgage comparison.

How often should buy to let mortgages be reviewed?

Buy to let mortgages are often reviewed:

1. At the end of a fixed-rate period
2. When interest rates change significantly
3. When rental income or property values change
4. When expanding or restructuring a portfolio

Regular comparison helps ensure the mortgage remains suitable and cost-effective.

Final thoughts

Mortgage comparison for buy to let is about more than finding the lowest rate. Fees, rental affordability rules, flexibility, and long-term strategy all play a role in determining which mortgage is suitable.

Understanding how buy to let mortgage comparison works can help landlords make more informed decisions, manage risk, and maintain control over borrowing costs.