I'll tell you right away that with a budget of 7 its going to be a non-turbo automatic version.
but for 7k this is still very hard to find, maybe if the car is a roller and missing the engine.
I've seen some Supra's sell for around 9k in bad condition and really high miles.
So your answer is yes you can find a Supra for 7k (even possibley less), but it will be missing the engien and transmission etc.
check out
www.supraforums.com classfields section, that's the best place to look.