If you have a previous bankruptcy or mortgage default on your record, lenders will be reluctant to grant a new mortgage. However, an occasional late payment on a monthly credit card bill will not disqualify you for a mortgage.

If your income is subject to fluctuations (for example, if you are paid on commission), the lender will qualify you on the basis of a conservative estimate of likely earnings. Self-employed borrowers receive particularly close scrutiny.

If after the down payment you will have less cash in reserve than you would need to meet three mortgage payments, the lender may conclude that your loan could go bad if you were laid off briefly or had some other minor financial problem.

The lender can choose to allow you to pay more than 28 percent of your income to meet mortgage payments. However, usually the lender must find some other factor in your favor. For example, if the new payment will represent little or no increase from what you previously were paying in rent or a mortgage payment, this may help. Lenders also take into account compensating factors such as a large down payment or sizable cash reserves.

If you do not qualify for a 30-year fixed rate loan, you may qualify for the same loan amount if a lower-rate mortgage can be found. However, few prudent lenders will use the initial rate on a short-term adjustable rate mortgage (ARM) as the qualifying rate. One rule of thumb is to use the maximum possible second-year rate. This often is below the 30-year fixed rate.