my motor problems

hey guys, i got my old 2.9l ford all torn apart and was ready to rebuild it, but i wasent sure if i wanted to put like 500 bucks into a motor when i can buy another used motor for like 150-200 bucks. what im asking is should i rebuild the motor or just get a used one out of a donor. keep in mind i have a very low budget and i need something fast

rebuilding it will be worth it in the end.