What is the minimum list of things I need to do to the car?
You'll need to check the rule book for the details on these.
- Roll cage
- Race seat(s)
- Racing harnesses for each seat
- Fire extinguisher(s)
- First aid kit
- Three safety triangles
- Towing points front and rear
- Tow rope
- Mud flaps on all drive and rear wheels
Really, that's it. Take a normal, running car, add those things, and it's legal to rally. There's some other stuff you need to do to the car but it doesn't involve buying anything. For example, taking out the air bags.