48V PWM Motor Controller
You can do it yourself or buy it. It's your decision. We don't know how experienced you are, so nobody will tell you what to do.

If you have no experience with any PWM motor drivers - you should mess around with low power motors first.

PWM regulator for 1000W/48V motor needs good overload protection, because it has to be powered from very low impedance source (big battery with short-circuit current probably over 100A).

In addition - regulator for vehicle must be able to handle voltage (or power) coming from motors while slowing down, because motors work as generators.

Edit:

I found something useful for you: How can I implement regenerative braking of a DC motor?