very basic rule of thumb, buy a house when the cost of the house you want is 3 times the salary you/your spouse make. Obvious variable being how long you want to live in that city. Less than 3 years, probably better to rent, unless you think the home will appreciate 125% or so. Again, very rough numbers, but in the navy I always made my home buying decisions somewhere along those numbers

EDIT: probably need to clarify the first statement, just because the house is 3 times what you make in a year, DOES NOT MEAN you can afford it, that is the upper limit of what the banks are looking at. You are better off keeping it less than 3 to 1 for paycheck to paycheck purposes.