120,000 miles on a 12 year old car is technically lower than average. Take it to a mechanic to have it checked before you buy... Remember, there has to be SOME reason why he's selling it... If it seems fishy, you obviously know what to do.

 

Check the compression and look for excess smoke (any smoke after the engine is warm). Blue is ok if there is a little, white is BAD, black smoke means its running rich

Just because someone sells a car doesnt mean its a rattted out POS. Maybe they want a TII.

 

Remember that a rotary engine is designed to smoke on startup, disregard a small amount of blue smoke for the first 2 minutes.

Also remember that rotaries do not idle well, even when in good condition; it will not sound like your mother's 95 Camry. As long as it holds its idle, doesnt die, doesnt make any unusual driving noise, and has a decent amount of power, its probably a good deal. 120k is average or so.

FWIW< the first rx7 I ever bought was an 89 gtu with 96k. I kept it until 113k, 2.5 years, and it was the most reliable car I ever had, including several chevies, and toyotas, and my friends hondas. IT was bone stock and well maintained, only had a midpipe adn k&n dropin filter and would run with a stock t2 if driven right.