Think about you want to do with it. Do you want to end up with a relatively stock TJ or a fairly built TJ? I ask this because I was always the guy looking for stock vehicles that I could build myself, my way...but realized after having done that more times than I'm willing to admit, you can buy someone else's hopes, dreams, and investment for pennies on the dollar....then just fix all the stuff that's not right and come out thousands of dollars ahead.
I paid $11K for a 1997 TJ with 120K on it. The clear coat and paint is peeling off the doors and hood, but it came with an OEM hard top, D44s with ARB air lockers and 4.88 gears, OMF beadlocks, and a bunch of other stuff who's prices, should I have bought them on my own, add up to nearly $18K. So, for $11K, I got 18K worth of aftermarket upgrades and a free Jeep. I couldn't buy one and build it like this for less than probably $22K. It's been a lot of work sorting out all the problems, but not much money.
If your end goal is a relatively stock TJ in decent shape, I'd expect to pay no less than $6 and up to $12 or $13K