We bought two SFs and one townhouse from 2002~2004, then we sold the most expensive one at peak price last year, and keep one SF as primary residence and one townhouse for rent now. We make money from RE around $250K, and have home equity around $350K. The lesson we learned is the time and luck. If we start the whole purchase from 2005, then you may experience negative equity at lease for a while.
Remember-Don't put most of your money in one basket!!!