Mortgage Shopping: How Do They Know What I Can Afford?
Most mortgage brokers will have software that they can plug in your income numbers and outstanding loans (as in loans you owe, not fantastic loans) and come up with a pretty good idea of what you can afford - in terms of home price and monthly payments.
However, it is always a good idea to take those numbers home and sleep on them so you know exactly how much you will be paying and if you can afford it month after month for about 30 years.
You can refer to this earlier post with mortgage calculators to get a better idea and calculate for yourself.