It varies from lender to lender but a good rule of thumb would be multiply a single income by four or a joint income by three then subtract any outstanding loans or credit you have currently.

A tracker mortgage is a mortgage where the interest rate follows the base rate set by the Bank of England. The rate you pay will not be the same as the base rate but will rise and fall as the base rate does. Therefore if the base rate drops, your payments will go down, if the base rate rises your payments will go up. This is different to a fixed rate mortgage where the amount you pay each month is fixed and will not change.

With an interest only mortgage you only pay the interest on the amount you have borrowed each month, you don't pay off any of the capital. If you borrow £100,000 for 20 years, at the end of the mortgage you will need to give the lender their £100,000 back. Therefore you must have a plan of how you are going to do this.

With a repayment mortgage on the other hand each month you pay the interest and a proportion of the capital you borrowed so that at the end of the term you have paid back the entire amount of capital that you borrowed.

Yes, even with a poor credit history you should be able to find a mortgage. The lender will view you as being of greater risk than average and you will therefore have to pay a higher interest rate than average, possibly higher arrangement fees and you will probably have to have a bigger deposit.

Self-certification mortgages tend to be taken out by the self employed as they can find it difficult to prove their income. With a self-cert mortgage you declare your income to the lender but do not have to provide evidence of it. The greater risk to the lender is reflected in a higher rate of interest.