I want info abt the motors for rc off road?

Actualy i am building a robot having a 3 lever joint with a 360 and a 180 degree rotation. So i want to know what type of motor is it suggested to use on them. like the rpm/? thought a 20rpm motor should do but i really dont know which 1 to choose. Plz help me with this i am realy in neeed of great help.Thank you