On the other hand, the S&P 500 returned 8.25% annually between 1993-2006. Say you put 10% down ($8500) and spend $800/year total on taxes, repairs, etc. (probably low). If you'd invested in an index fund, you'd have made $42,000.
And also likely have moved several times at an average cost of around $2000 per move, seen rent increases above what his current mortgage is and so on. The odds are poor that all other things would have remained equal. I owned a house at one time. I benefited by about $2000/year over the time I owned it. When I refinanced, I got my escrow back and had no mortgage payment for a month. Then my payments after that were lower. No landlord in the world is going to drop by your apartment and leave you with a nice hefty check, say "Don't bother to pay me rent this month and, oh, next month your rent is going down. Cheerio!"