how much FHA loan can you afford...
For an FHA loan, your monthly housing costs should not exceed 29% of your gross monthly income (what you earn before taxes and other deductions are taken out). Total housing costs include mortgage principal and interest, property taxes, and insurance. Those four terms are often lumped together, and referred to as PITI.

example
Multiply your monthly income X .29 = Maximum PITI

For a monthly income of $3,000, that means
             $3,000 x .29 = $870 Maximum PITI

Your total monthly costs, adding PITI and long term debt, should be no more than 41% of your gross monthly income. Long term debt includes such things as car loans and credit card balances.

example
Multiply your monthly income x .41 = Maximum Total Monthly Costs

For a monthly income of $3,000, that means
            $3,000 x .41 = $1230
$1,230 total - $870 (for your home) = leaves you $360 for monthly long term debt

The ratios for an FHA loan are more lenient than for a typical conventional loan. For conventional home loans, PITI expense cannot usually exceed 26-28% of your gross monthly income, and total expense should be no more than 33-36%.