That's wonderful that you had such great experiences with your rescues, good for you! Unfortunately, judging from my own experience and the dozens of threads on this message board, your experience puts you in a minority.
To the OP - If you were my riding student or a client in my barn, I would steer you away from the rescue route until we had thoroughly explored other options. I would want you to have a known quantity, a horse whose history I knew and somehting that would give you a safe and fun experience. Depending on your location, and because of the market right now, you can find horses like that from 0 - $1500.
If we weren't finding good options in your price range, I'd look at rescues, but I would very diligently screen out maintenence, training and soundness issues, and insist on one that was novice safe under saddle.
It's great that you're asking these questions now; before you start looking. Good luck with your search!