Should i use 1 or 2 motors for a lift?
This question is far too vague. What is the purpose of said lift? what is its geometry? How large is it? Is it a 4 bar? Double reverse 4 bar? Something else? What are you lifting with it? How much does the lift weigh? is it steel or aluminum?
Please read this:
Bruhicus momentus
20 ch
4 Bar aluminum lift. The purpose of it is to lift mobile goals up and onto the platform.
1 motor with a sufficient ratio would easily support that, even without rubber bands.
but please use rubber bands 
1 motor is doable, but I have encountered instances of where the side without the motor would lift unevenly. I would recommend running a HS axle across to distribute the torque better.