Allright, i own a 1991 5th Gen Celica GT, Red HatchBack.
things to look out for.
Cluch: on my Car when i got it, it's cluch wored fine for a couple of months. but the throw out was making noise. so when the cluch started to give out i had it all done.. well aparently my cluch still have plenty of life on it, yet the throw out baring was shot to shit. so keep that in mind.
Oil: if it leeks, dont buy it. not worth the trouble. (that go's with any car) but i have to say my 168k Mille Car dosent leek a drop. another thing is to look out for the "sludge" problum, i dont know the details on this one tho.
oil leeks to be expected: around the distributor, but thats nothing to wory about.
I highly recomend you get the car up on a lift before you buy it. once thing to look out for when u do this is Rot on the tub. u wont see it, but puting it up on a lift will tend to crush that location down. (its no bigie if its minor) but its another thing you can check for.
now Celica's of those years tend to get niglected as far as maintance go's so make shure there's a clean air filter in there and none of the PCV or another other Vacume lines are Heavly Cracked.
Brakes: the car has drums in the back, make shure you check them, BC you might not know it but you may need new shoes.
once you do own it, change the oil evry 3000 miles and you can expect it to hit +200K Milles.
i get 22-25MPG with the car.
Mods: Swap in a 3sGTE mottor and your done
if thats not ur cup of tea, or within your budget hear are some alternitives.
Cold Air Intake (300ZX's CAI should fit the car well, do a serch on TN for that), get Headers for the car, there out there, just hard to find. have a decent 2.5" exhaust "MADE" for the car, none of the aftermarket onces are worth bolting on. use a universal muffler and rezinator. get a inline Cat for the car, thats high flow and intended to work futher down streem from the head.
Or
Get a Toyota Made CT-26 Turbo Charger, the Exhaust Mainfold off of a 3sGTE, and the Turbo 2Bar MAP off of a MR2 Turbo, and Some Costom piping and u got a trubo setup for around 1000 bucks. (depends on the price of parts)