We started with a small camper trailer, 16' with a small bathroom, pulled with an F150. We barely got up some steep hills in the mounains, going slow with the heater on to keep it from overheating. It was fine for the first summer when we lived outside much of the time anyway. Not long after we went bigger and bought our basic 5th wheel and also an F350 to tow it. No more towing problems.
We still find the basic 5th wheel to be a bit too small for long term living and might buy a bigger one with slides the next time we upgrade campers.