It looks like you need to know the family's total annual income to know whether they will be able to afford the place and if there will not be any difficulties with payments. At first, you can ask for some bank statements that would confirm that one or several family members earn enough and have a stable enough job position to ensure that there will be no unpleasant surprises. And then, you can take the papers to Mortgage Broker Hull or a similar company to make all the exact calculations and make a contract with the tenant(s). It doesn't sound very easy, but it gets easier when you do it more than once.
