$50 garage sale find

I bought this at a garage sale for $50. I really know nothing about it other than it’s a Trek lol the seat tube is 19” from center of the crank to the top of the tube and it has 26” wheels. My plans are to do a budget rebuild, including a new fork(this one is frozen solid) new cables rear derailer(this one is junk) and a single sprocket crankset. Does anyone have any recommendations for any of this stuff as well as what exactly I have? Thank you all!!