Step 5: Motor
I bought my motor for $50 out of some guy's garage. He had bought a junky forklift to build his own automotive lift, and had no use the the motor and some other parts.
The motor was very rusty and greasy, but it did spin (not fast or easily) when I applied 12 volts to it.
Rebuilding an electric motor is very easy. There are only a handful of parts to it.
I degreased it, removed the coils and sprayed them with insulating epoxy, checked the bearings, put it back together, and painted it.
I also had the machinist put the rotor on his lathe and take a tiny bit off the commutator. That makes it looks new, and provides a smooth, conductive surface for the brushes to ride on.
I also replaced the brushes, purchasing new ones at a shop that specializes in forklift motors. $50 for the new brushes brings the total cost of $100 for a pretty decent electric motor.