I have to agree with Flyin'.
I am an incurable romantic and feel that all MK II Supras should be rescued no matter how much time, effort, and money it takes. I spent the best part of $8,000 for rust repair and a bare metal respray, and that was after I performed all the labor to disassemble the car and remove the interior. But I've owned the car since 1987, and plan to keep it until they take my driver's license away, so it was worth it to me.
It makes me very sad to see a car left outside in the weather in this condition. Rust has most likely formed underneath all that Bondo. Any car can be restored, but unfortunately this one would have to be a labor of love, and a long labor at that, done by someone experienced in body work, as well as someone with a lot of spare time and financial resources. It is not something you are going to accomplish in one summer before going off to school. I can tell you from personal experience that when the fender flares are removed, there is going to be lots more rust as they trap dirt and moisture between the flares and the steel body. Since there is no source of replacement panels as with a Mustang, Camaro, or MGB, new sheet metal is going to have to be made by hand. And all the corrosion has to be completely eliminated, or it will just return. You can't just cover it with Bondo and repaint it. It can be done, but takes a person experienced in body work with all the proper tools and an enclosed, heated space to work in. If you scrounge, replacement parts can be sourced, but they maybe far away from you, and therefore costly to ship.
An upholstery guy/gal can help restore the interior panels, and seats, for big $$$. There is even a service that can make a new dash cover, also for big $$$, but it will not have the original grain or fake stitching. You also said there is a mechanical issue with the engine that would require attention.
As much as it pains me to think of this car sitting there rusting into a pile of dust, my advice would be to stay away, unless you wish to keep it for a long time and have a dry space to store it while you are away at school. Sorry to discourage you in this, but that is the reality of it.