Here's gwern's excellent and sobering commentary.
Alright, here's a kid with IQ 70. He can lift things under 40 pounds and put them where you tell him to. I'm afraid he can't read past a third-grade level, or anything like that. It's probably not a good idea to let him near any moving machinery either. Fortunately for you, he doesn't throw any violent temper tantrums and he doesn't steal - he's a sweet kid, willing to work. Just dumber than a stack of bricks. Take him down Main Street and see if anyone will hire him. How many job offers did he get?