Would you teach your daughter to drive in a 6 speed Corvette? What about a hand built street rod? I wouldn't....
What you really want is a super durable low HP durable airplane, and they make those, they are called Cessna 150/152/172's.
I bought my 150 for $20k, hired a private instructor, got my ticket, flew the airplane for a total of 100 hours, and sold it for $20k.
This did a few things:
1. Avoided rental fees.
2. Provided me my first airplane ownership experience on what is arguably the cheapest and most reliable airplane made.
3. Gave me something that was easy to fly to start out with which accelerated my learning.
4. Saved me TONS of money on gas. I burned $12/hr (mogas), not $30/hr (assuming the RV wants avgas), and in that first 100 hours saved $1800 just in gas.
5. Taught me what I really wanted, which is a tailwheel bush rig. (I live in Alaska)
Notice I didn't even touch on insurance or other things that matter....
I would never recommend an RV as a first airplane, but it's a very good choice for a second!