Hi C.,
I am not in real estate or loan markets, but when we purchased our first home in 2002, we didn't listen to the realtor nor the loan officer on the loan we could get. I took my AFTER TAX income and decided what we could afford a month for a mortgage based on that figure. I also wanted security so we went with a 30 yr fixed (even back then I didn't want to chance the rates going up on an adjustible rate mortgage). Also, the first year is always the hardest because you don't get the benefits of the interest on your tax returns until the following year - you can get a lot back - unless you adjust your payroll deductions when you purchase your home. Also, don't forget to figure in costs like property taxes, home insurance, utilities, general maintnance, etc...
Again, I think the most important thing is to base what you can affor your net/take home pay.
Good luck!