boyweld
For the price range you are talking about, eBay may be your best bet, or craigslist for a good used unit. Be very wary of the new Chinese machines offered there, some are decent, others are pieces of C**P.
Unless you have someone who is knowledgeable on those machines to help you, you are better off sticking to a known American brand name.
I personally am biased against combination cutter welders, I find the ones I have used, do not do either job very well, they work , but that is about all you can say for them.
Spend a bit more money and buy a dedicated welder and a dedicated plasma cutter.
B.E.