Frugal Living
I got this from http://money.cnn.com/galleries/2008/moneymag/0801/gallery.midlife_checkup.moneymag/index.html - click on the OWE icon
28%: Devote no more than this amount of your monthly pretax income to your mortgage.
75%: By age 45, limit your home loans to this portion of your home's value...