When we first bought our motorhome, we rented because neither vehicle we had could be easily flat towed. We'd stop at the rental place first to pick up the car before going to the campground. I'd drive the motorhome and the wife would drive the rental. It worked out pretty well. We probably spent about $500 in car rental fees and the occasional taxi.
Then we finally got a vehicle we could tow and had every intention of setting it up to flat tow. We eventually decided we really didn't want to spend the extra money to outfit it and purchase a tow bar and aux. brake.
If we needed a car, the wife would drive behind the motorhome. Except for our seasonal trip which was about 12-14 hours depending on traffic, we usually stayed within 5 hours of home when camping, so it wasn't a big deal. Almost half of our camping trips a year were to Disney's Fort Wilderness, where we didn't need a car anyway.
Now that we no longer own the motorhome, I am glad we saved the money. All told, we ended up saving a good bit of money not flat towing. If we took more long distance camping trips, it would have made more sense to flat tow.
-Michael