If this is an option that you still find intriguing after all this odd advise, then it is still worth exploring. I recommend sliding on over to the full timer forum and asking there. It seems some posters here don’t realize that full timing is a thing.
If I were trying to do your plan, I would find an owner who thought full time RVing would be great a year or so ago and now realize that it is not their lifestyle after all in the hopes that they are trying to get rid of a high quality fifth wheel for a reasonable price. In my fantasy world you would have the best of both worlds…….a quality full timing RV in the price range you are looking for.
Good luck, I think it would be awesome to raise kids in a campground if I could find the right one. Security is generally not a huge issue, though I suppose there are places where it could be. One advantage, if you don’t like your neighbors, it is not too difficult to move.