I would agree with getting a good clean shell for a swap....... Say you spend the 500$ for the RUST BUCKET, About a 1,000 for an average CLEAN shell. Then throw some money at the engine to get it running and your set! Maybe just over 2,000 bones and you have a great car in an easy 6 months.
OR
Get the RUST BUCKET for 500 spend another 300 on a decent welder, another 400 for some sheet metal and welding material, add LOTS of time! then you still need to get a good engine another 500.........ect. in 6 months you would be lucky to have the body straight.
It adds up FAST!