Is it worth the buy?

Check and see if that engine is considered an interference engine which it almost certainly is. An interference engine means that the valves can contact the pistons when the belt breaks. Bent valves means a expensive re-build of the engine. There is a reason why the car is cheap!

Do a compression check. Any cylinders having 0 psi will have bent valves. Not that bad of a fix for someone that is handy with tools and an attention to details. but a shop will charge you a thousand or more to fix.

Where is this car located? I could always use another parts car.

Yeah bro 500$ sounds like a good deal from the person your buying it from! If the belt broke you may have bent valves broken pieces and maybe bad valve seats

If TB broke "at speed" best case, valves are bent. Worst case they went through the pistons and/or damaged the block! If the block is ok, fixable , but not cheap.

Funny. Situation I just faced on my 95. The tensioner pully some how backed off creating NO tension what so ever on my water pump system? And I had a occasional hesitation after driving 5 miles then went away THEN IT starts to over heat about four dots part the regular normal heating gauge. So I stopped driving it I didn't discover a this till I pulled off the front timing belt cover facing the front of the car It had some serious slop in the belt. So how can a hydrolic tensioner just stop creating tension making slack in the belt?

I wanna get this 3000gt but it’s a 92 and it has 180,000 miles on it he selling it for 1500 should I

Check compression on the front heads where it is most easy to access. That will tell you everything. Should be in the range of 180 or better if not it needs to be rebuilt imo. I had one that compression was 150 - 175 it drove fine but not much power. You can either buy a good reman for 3500 or build one yourself for less but if you dont know what your doing i strongly suggest having a experienced mech build one for you. Buy only oem spec gaskets multi layer type