hi tjn...
Given a $500 budget... if you can find nearby Cyclone II or old Tornado Coin Op with "fair/good" cabinet & rods for 300 or 400 you'd be in range for a good good value.
Fair or good cabinet would be one with "flat/non warped playfield". Straight and solid sidewalls & end walls (no beer spilled swollen sidewalls & not dead end walls where the ball doesn't bounce off crisply).
Fair or good rods will be mostly straight and not wobble when spun. Avoid lots of rust/pitting on the rods. With a new rod being $40 plus... you'll not want to have to replace more than 2 or 4. (maybe just your side & let your opponent deal with old rods!).
Best thing about getting a deal on quality Tornado cabinet.. is the quality of parts you can get to tune up a good table/cabinet/rods with new parts to get premium play out of your table. About $100 will tune up half your men/bumpers/bearings/pins... check out the kit at our shop...
http://shop.foosball.com/tornado.html The Tune10 kit works well for getting shooting rods dialed in best play.