Hi @David G., we have 2 tiny houses in a rural area south of Houston that we rent on AirBnB . It seems that the issues with land, sewage, etc. would be very specific to your location. Tiny houses on wheels usually qualify as RV's, so that simplifies things regarding permits and sometimes whether they're allowed to even be there. Some municipalities have minimum square foot requirements for housing, and tiny houses don't qualify.
This is a little detail, but one problem we've had is that tiny houses have tiny water heaters. I tell the guests that "speedy showers are a necessity". I wonder if the note in our listing about limited hot water discourages some guests from booking, particularly those who'll be staying longer than a couple of days.
This winter, we had a hard freeze, which pretty much never happens here. Since the tiny houses are up on trailers, it was hard to adequately protect the pipes, and they did freeze. We also had difficulty getting the tiny houses properly connected to the septic system, and that was a headache. So, that's just normal issues that you have with rental properties, but the trailer thing does add another dimension to it.
When we decided to add the tiny houses to our Christmas tree farm, we had to put in a road and a septic system and run electricity and water out to the location. It was expensive, but we put in connections for 3 houses. We currently have 2 houses but hope to add a third eventually. We stay booked most weekends, with some longer stays. It's rare that anyone stays longer than 2 weeks.
Good luck on your venture!