In the US, you have fixed-rate mortgages and adjustable-rate (ARMs). Fixed rates are usually 15 and 30 years. The longer the term, the lower your monthly commitment, of course. I believe a 30yr fixed rate is probably the most common type of mortgage. I don't know the details of the ARMs, but a lot of people were suckered into those which is why a lot of people are having huge problems, these last few years. If you get as much or more house than you can afford so that you're just getting by every month and a few years down the road, your rates jump, you're screwed.
My fixed mortgage is fixed for the life of the loan (until 2040), so over time, the percentage of my income dedicated to paying my mortgage will continue dropping.