Can you park the cart at various sites to look around and get back on and continue your trip?
The golf carts are charged by block of time. Really, you would not want to be paying that much to leave the cart parked somewhere.
If your concern is getting around the grounds, there is a shuttle system that is made to look like small trains (not trains, just look like them) that will ferry you from the grounds back to the Trianons. When I was there on a crazy busy day in August, the lineup to catch one of those trams was probably about thirty minutes long... long enough to walk there by myself.
Edit Despite what I said above, I found a page listed here that discusses the golf cart at Versailles. They say that it is seven euros per fifteen minutes, but that was as of September 2007 (probably more now). If you stop to tour around, you will be about two hours (I say that is a bare minimum) which will be 56 euros.
Marie, it's not a problem to park the cart to look around. Versailles is a huge place...the real advantage of a cart is it allows you to cover much more ground than otherwise possible. The only other way to see a lot of Versailles is to get there bright and early and spend all day (or two). If you have kids the carts are really the way to go.
Don't forget to bring your driver's license.
The carts have very limited areas and routes you can go. You can't just amble anywhere (eg, the domain of Marie Antoinette). Check these limits before you pile in and head off. If you rent a bike, you also have to leave it outside the domain. When we tried to rent a bike, the fellow never showed up at the rental stand that day.