Affordable loan amount = the present value of an annuity based on the annual income when you buy a house in the future (actually, it is your annual income when you buy a house. For example, if you plan to buy a house five years later, then the present value of your annuity is Your income in five years) * The upper limit of the affordable loan ratio in your annual income (how much of your income you are prepared to use to buy a house, and what proportion of this money accounts for your income)