Not sure what I can add. You got some good input here already. I'll just share my personal experience: I broke every rule. I bought new, I financed it, and I bought larger (36ft). I never practiced backing. I purchased from a dealer a long way away (100+- miles) because they had a great price for the unit I wanted...
The first time I ever towed anything close to this large was the day I picked up my new unit at the dealer. My first towing experience was first on the interstate and right into a small town with tight turns to our first campground for the shake down weekend.
Yes I curbed it once that first day. Not since though. I got a pull thru spot for that first weekend, so my first chance to back it up was back home at the storage lot. Anybody watching would have been in for a great deal of free entertainment... But it was good practice LOL...
I'm 100% not saying that everybody should just wing it the way we did, but I had sense enough to know that I was new, took it slow, kept the right attitude about the whole thing. We learned fast, did fine, and had a wonderful first outing.
I do believe in buying the second (or third) camper first. This takes a lot of research and thought. If you go long you might shut yourself out of some camping areas. I have not had this happen so far.
Best of luck and make it fun! We were just like you. Enjoyed camping as kids and wanted same for ours. Not one regret here - except waiting as long as we did to go for it.