Buying a Used Prius

I find it very hard to separate the wheat from the chaff in looking at used car ads in ebay, autotrader, car.com etc. I'm pretty sure I'm looking to buy an early Gen II as that's what my budget requires. But, most ads don't specify which model or package the individual car has, only a list of options. I assume the higher the package the higher original sticker price. Correct? I also see cars from the northeast and some of the northern midwestern states seem to have the lowest prices. Is there a reason for this? Is it a wintertime salt on the roads thing? Florida, my home state, seems to have very high Prii prices? Any rational reason for that?

Anyway, I'm looking to get the most bang for the buck with an eventual goal of turning the car into a PHEV. I had hoped to do all this for approximately $20,000, but I realize that's maybe a little low. I don't mind doing a little work on a somewhat tired Prius as I was a mechanic and electronics tech in earlier lives. While I don't paint myself, I have a crackerjack painter buddy. Any ideas? Leads?

P.S. I've been dikin around modding cars my whole not so short life.