Don't get fooled by billy's appearance. He's a celebrity in the wastes for his amazing mechanic skills. Did your car ran out of bio-fuel, got burned down by bandits, or crushed by a giant mutant ? This good boy will bring it back to life in no time, as long as you have what to pay.
His business got in even better shape when he took Fifi under his wing for assistance. I mean, he has no wings... nor arms actually. But don't let that trivial detail deceive you. The guy knows what he's doing.