I had an 93 RX-7 right before I got my WRX. It's make a great project car if you have the money, but the single biggest thing you need to get checked out is the motor. And you need to get it checked out by a good mechanic who know's 'em well. It's quite easy to buy an FD with a blown motor and not know it (water seal leak, weakened apex seals). I know because that's what I did. Mine had a water seal leak and needed a motor rebuild ($5k+ done right)

That low price on the RX-7 can likely hide a problem that the owner is not disclosing because there is still a HUGE demand for these cars. When I sold mine a year ago I had it on autotrader.com and I was getting 3-5 emails per day and phone calls from all over the country, so the price isn't because he's having trouble getting it sold.

If you're seriously interested in it, have Ivan, the bay area FD Guru who lives in Sunnyvale check it out for you. PM me if you want his number and I'll dig it up.

If you do just want to check it out yourself, then there's two things you should do: 1.) pull one of the plugs and do a compression test. Compression should be same across all 3 rotor chambers. If two are lower than the others, it could point to a weakened seal. 2.) take it to a smog shop, pull the radiator cap and get the guy to stick the smog probe in or close to it. if it finds hydrocarbons, there's a chance it's got a water leak. That and also check it out with a cold start. If white smoke comes out as it's warming up, it's another bad sign.