What is a mortgage in principle, and how do I get one?

What it is

A lender or broker takes your basic details (income, outgoings, deposit, a soft credit check) and gives you a written figure for how much they would be likely to lend. It takes 15 minutes to an afternoon and usually lasts 60 to 90 days.

Why you want one before you view

• It tells you your real budget, so you look at the right houses.
• Estate agents ask for it. Some will not put your offer forward without one.
• Sellers take your offer more seriously than a cash-free "I'm sure I can get a mortgage".
• It flags problems early: if a lender will not give you one, you find out before you fall in love with a house.

What it is not

It is not a mortgage offer. The full application checks your documents, your bank statements and the property. Things that can turn a yes into a no: the valuation coming in low, something on your statements, a change of job, or a different property type (new-build flat, non-standard construction, short lease).

Where to get one

Directly from a lender's website, or through a broker. A broker's version is more useful because it is based on the lender most likely to accept you, not just the one whose website you happened to visit. Ask whether the credit check is soft (invisible to other lenders) or hard.

What you need

Income, employer, how long you have been there, monthly debts and commitments, deposit amount and source, addresses for three years, and permission for the credit check. No documents at this stage.

A note on the numbers. Thresholds, schemes and typical costs are correct as far as we know at the time of writing and are for England and Northern Ireland unless we say otherwise. Rules change and lenders differ. Check the current position, and get advice from a qualified broker before you commit.