We bought a small pop-up, but only used it a few times before we sold it. It was just a pain to set up and take down. We really just wanted to pull in and start camping, but instead, the first hour was spent fiddling with setting it all up.
A slide in might be nice, if you have a big truck. Only bad thing about those are, when you go to the store or out exploring, you take your whole rig with you. Maybe have one of those easy-up shelters to mark your campsite.
Our retirement plan is to get a used Sprinter style van, and convert it to a camper. Then for at least a year we will just go "that-a-way", wherever the wind takes us. Probably try to hit up as many Nat'l Parks as possible, with a bunch of State Parks thrown in. We have kids in Florida and Nevada, so taking different routes between those 2 end points will give us plenty of opportunities for adventure.