A smaller FW that can be easily pulled with a gas truck will keep the truck cost down considerably. For towing a camper 4wd doesn't matter much. For launching and retrieving a boat I would want it. Around here we have mountains and it snows so you rarely even see a 2wd truck and it's hard to give one away if you want to get rid of one. I use my truck for all kinds of construction, firewood, etc. so I won't be without 4wd.
I can find lots of gas 4wd HD pick-ups for $20,000 that I would consider reliable but that's kind of subjective. As for a FW, just depends on what you want. A small low option unit is a lot different than a 40' luxury model.