It's not cheap to motorized. I suggest get a set like 9398 or 42099 to built it yourself. Then study the servo, drive, suspension, link-arm, bushes, axles, rods, etc.

There a quite a few modders and e.g. you can try search for Sariel.

If you expect to zoom around like RC cars, you are in for disappointment.

My old video motorizing Unimog 8110 (2nd favourite modded).

#1 Testing XL motor


#2 Testing servo/steering mechanism


#3 First trial run


List of parts, just search the breakdown list of 9398/42099 in BrickLink to find the remote, IR, motors, servo, etc. and you get the idea of individual unit costs.