buying used motor

well the thing is i am finacially challenged so should i bite several bullets or not, i know i need to get you guys #s on motor and plan on doing this over the weekend but what i am looking at is i have a tired 318 in my dart and want to rebuild one on the cheap so i am at a disadvantage at throwing money at it i dont have i know it seems like a good deal but i cant hear motor cause its out of car any tips would be great