I have a gasoline powered, Kawasaki 4010 Trans. It's not a perfect machine, but works well for what I ask it to do.
I like the 4010 trans series, as you can either run it with two bench seats for up to five (six if they are small) and a fairly decent box or you can fold up the rear seat and expand the box and cargo area. It has 2wd, 4 hi and 4 lo. Now, they are not speed demons in any sense, I think top speed in them is like 26 mph, but they have excellent torque and traction. I've used my several times to skid black locust logs of 20 feet long out of our property.
One misconception people have is that a side by side should be able be a work horse and an off road racer. It's not going to happen. You'll need to decide which is more important to you, the utility or the sport side of things. A utility utv is not going to be fast, it's not going to have huge ground clearance or massive suspension to handle the jumps of off roading and back country driving. A sport utv is not going to be built to haul your tools, it's not going to be built to work, it's for fun.
Another thing to remember is as
@sonya123 said, people use the hell out of these things. If you aren't versed or wanting to work on them, you're better off buying new. I bought mine from Iron Planet, it was an ex- Sunbelt Rental machine. I spent quite a few evenings working on it when I purchased it, just to get it to run reliably, but, I own a repair shop and am pretty handy with machinery, so my time and experience saved me several thousand dollars.