I think those are called golf carts.
I got a free one (100% tax credit) from the state of Arizona in 2000.
It was a GEM car, and essentially a glorified golf cart like you say.
I got 1100 miles out of it before the batteries failed. New batteries were $1600, quite a high per mile operating cost...:^)
How hard is it to convert one to use a 5hp Briggs and Stratton engine?