A potential borrower can use an online mortgage calculator to see how much property he or she can afford. A lender will compare the person's total monthly income and total monthly debt load. A mortgage calculator can help to add up all income sources and compare this to all monthly debt payments. It can also factor in a potential mortgage payment and other associated housing costs (property taxes, homeownership dues, etc.). The typical mortgage calculator does not include costs like maintenance costs, refurbishment, landlord insurance, and other extra costs like service fees, property management costs, etc. One can test different loan sizes and interest rates. Generally speaking, lenders do not like to see all of a borrower's debt payments (including property expenses) exceed around 40% of total monthly pretax income. Some mortgage lenders are known to allow as high as 55%.