As Supras are old cars now there are plenty of them out there that could do with a bit of back to metal TLC, though from their exterior you'd probably never think that. That's both the good thing and also the not so good thing about the car, it still looks good after 20 years and hides nasty things like rust very well.
If you are good enough and brave enough to tackle anything then there will always be the car that needs a lot of TLC coming up at relatively cheap prices. One of the main issues with tackling a project Supra these days is availability of new old stock parts as more and more are discontinued in the OE supply chain by the day and Toyota has been ramping up prices of whats left. So new parts, if they are available, have become very expensive to where they were a little over 5 years ago (tripled on some parts) and this price inflation has fed through to recycled parts to. These cars are now not just expensive to buy compared to just a few years ago but also quite expensive to refurbish especially if your set on OEM.
There are a refurbishment and rebuild threads from members in the Supra Chat and Projects sections here so if you give those a trawl you should be able to pick up on what to look out for with a Supra.
Good luck with your search.