Part of the "big as you can afford" is not just the size of the RV but the size you can afford to store, pull, insure, and rent for campsites. The bigger the camper, the larger the insurance bill, the larger the campsite bill (full hookups with 30 amp vs 50 amp, etc. verses a site with just electric. which is all optional but nice), the larger the fuel cost to pull/drive as well as larger vehicle. So, make sure you check all that out. If you're storage site will only handle 25' max, and you can't upgrade that, don't buy a 26' camper. That extra foot may wind up costing you another 25' worth of camper.
Fortunately My parents have a large side lot, where I can park ours, and we have a vehicle that's large enough to pull what we're getting. The part I didn't think about, was insurance. It's much higher on the model we bought verses the model we had.