As an owner of rental property and an owner of a tow behind camper this thought has crossed my mind several times. ...but when I think about how much work it is to prepare myself for a camping trip, and how much has gone wrong with my multiple campers in the past it doesn't feel worth my time for a couple hundred dollars.
Most campers are really cheaply built, and a lot can go wrong, especially for a renter who has little experience camping. Just among the crew that I go camping with here's what I've seen happen just in the past 2 years:
Canopy on a hybrid trailer came loose and flew off in a storm
3 different tire blowouts
fridge door flew open going down the road (latch broke), damaging the fridge, countertop, and food inside.
Slideout broke and got stuck open.
Water heater element fried from not filling with water prior to turning on the heat
Water heater cracked from not draining properly in the winter
Pump fried from leaving it on prior to closing up the camper then draining the lines at the dump station.
Blackwater valve broke, spraying sewage all over somebody
Charging converter went out
Cable for pop up broke
2 people had roof leaks
I could probably go on, but you get the point, there is more maintenance with a camper than a house or apartment, and if someone isn't familiar with that particular trailer it's easy to screw things up. I think about the time involved in getting my camper out of storage, showing somebody how to hitch it up, fill it with water, turn on the pump and water heater, operate the fridge off of gas, hookup the electrical, and then drain everything when done. It just seems like a hell of a lot of hassle for a small amount of money. While overall ROI is probably great because your initial investment is low there will be a high hassle factor.
In any case, I'm not trying to talk you out of it. If you have the time and tolerance I'm sure a person could make a significant profit. I'm just trying to make sure you realize all that is involved if you aren't a current camper owner. ...and I"m sure the teardrop style camper has a little more simplicity than some other style campers and maybe would be easier to maintain and teach someone to setup. It could be a great way for someone to start and earn some side hustle money to grow something bigger in the future. ...but if you have the capacity, to buy some real estate, you'll not only get the cashflow, you've got the potential for appreciation growth and tax advantages.
Just a few thoughts, take it or leave it. Again, I don't want to scare off the idea, you certainly could make some $$$ doing this, just playing devils advocate and making you think about all aspects.
I should add, I've had several friends who have rented campers to camp with us, and they've enjoyed the experience and have said they'd do it again over buying their own camper. There's definitely a solid market for this.