My MKIII wasn't my first sports car at all.. I had already been through a Porsche before I came across the Supra... and lets just say it would have been CHEAPER to get my Porsche fixed, than the Supra that I am fixing now. I even did the proper maintenance required when I first bought the car as well.... that is the saddest part. I bought the car for just over 3 grand, and took it into my local mechanic the day after to have the timing belt replaced, transmission fluid flushed, trans mount replaced, and all the smaller things that you could do to it. Its a real shame that I never noticed the fact that the valve stem seals were shot... because the engine ran in perfect harmony... until it died on me on the highway.
I am in college.. and thankfully I could afford another vehicle once the Supra went... I am putting a new engine into the Supra... and its killing me. All the time and money I have put into the Supra is just unbelievable... don't get me wrong, I love the car, but its been a huge moneypit.
There are several other cars that you could get for 5 grand. In fact - I bought an 88 Blazer for only $600 - and it has gotten me everywhere I have needed to go - without any maintenance other than fluids. Now I realize its not a desireable vehicle - but the point of the matter is that you could get something that gets the job done, for a lot less money.
If you want to find a really nice vehicle for 5 grand that is still fun, and rwd or awd - your best bet is to ask around, and look online - and be willing to travel to go find yourself the best deal. I had to travel a little ways to get the Porsche that I had bought - and it was only $1800 - and trust me, it could handle all the hell I put her through - the only reason that car went out on me is because I let it go with a problem that I knew about, and didn't have the money to fix. I simply let it go too far...
So the final answer is - you can get a Supra if you can find one for 5 grand that has already had all the proper maintenance - go for it. Otherwise, find something else.