The main difference between the residential mortgages in terms of accessibility criteria, such as a buy to let lender is more interested in the property rental potential of their personal income. Most want to be sure that the rental value may be less than 125% of the mortgage payment, if this criterion can be slightly different depending on the lender to go. Most but not all require a minimum level of personal income, something between £ 10 000 to £ 25 000 per year.