Earlier quoted context omitted.
The target customer is people with extra land who would like to put up an ADU on their land to make extra revenue from AirBNB. It could probably pay for itself within a year.
within a year? probably pretty aggressive goal. Cheap case, $50k for the unit, $10k all setups (really really conservative). that's $5k revenue per month, or ~$165 per night averaged. Yes, some places could rent for ~$200/night, but I doubt you'll have 100% occupancy rate.
Besides, as an Airbnb rental it would definitely pay for its own mortgage over time.