If you buy an RV, then of course you'll also have to buy insurance. If you rent, you may be tempted to let your existing driver's policy cover the RV. While there's nothing wrong with that approach, you might benefit from having a chat with your insurance agent to find out exactly what your existing policy would cover.
Will it cover dings and scratches? If you need a 70-mile (113-kilometer) tow to the nearest RV repair shop, will your policy cover that? It probably won't cover mechanical breakdown, though that is one option that the rental company may include -- you'll definitely want to discuss that topic with the company before you're facing down a tow-truck driver with a $1,000 invoice.