I'd fall into the buy one and fly it catagory. Renting makes a lot of sense if you make sure you rent a LOT to build time...but for some reason, many renters find excuses not to rent and end up not flying as much as they might. At $100 a flight, its easy to say eh, maybe next week. The irony is that Owners seem to find every excuse to fly. There is nothing like driving to the field, walking out to your tie-down and zipping around for 5 minutes or three hours. Even thought the plane set you back a load, once you have it, you WANT to justify it and use it. And there is no minimum flight requirement. If you only feel like doing 3 take-offs and landings and calling it a day, you don't have to worry about the FBO setting a minimum hobbs time.
If tailwheel is your thing, get a Luscombe, C-120 or C-140 or other antique TD with similar traits. They are CHEAP by comparison to most of whats out there. 20K will get you a nice one. Don't waste money on Nostalgia (ei, over priced Cubs for 40K). Don't Hanger it and don't feel guilty because its not hangered. Modern wing coverings can last for a loooong time outside. Anyway, find something in the 18k to 25k range and build time. All of the planes in this catagoy burn about 4.5 gal so you can fly a LOT and build time.
Then when it comes time to get a motor for your RV project, sell off the aircraft to fund the motor.
Really, its hard to go wrong either way renting or buying, so long as you FLY a lot. Its all too easy to just let the license lapse and find reasons to not waste the money. Every pilot has done it. Owning kind of forces you to keep at it (but it can also bust the bank if you are not blessed with the discretionary)