I would start with a single engine first, The trainer of choice at my club is the Sig Kadet LT-40 http://www2.towerhobbies.com/cgi-bin...1&I=LXFG19&P=7
It flies very well and rights itself very well and is fairly aerobatic with more control throws, Used planes are kind of pot luck, Lots of times you end up buying someone's problems instead of a good plane unless you know and trust the seller. One thing to keep in mind when buying is to get a good engine because if you get one that is proned to problems you end up spending all your time trying to get it running right when you should be flying, My choice is OS FX engines but there a little more $$$$ but run great right out of the box and have plenty of power but there are some other great engines too for less, I've never had one but I've heard Thunder tiger engines are good ones too. Can't help you about the twin, Never even seen one fly but I do know there are a lot more issues with a twin that should be down the R/C road for you, Like if your 2 engines are tuned different of set at a different speed it will turn possibly going into a flat spin but I'm sure someone who really knows about them will respond.

Best of luck
Dauntae