Nicolas McNaughton, Seth Williams
I've been working through these same ideas! I think AirBNB/VRBO is a great option if you live in a popular area. You can check out AirDNA.co and get some rough numbers on what an AirBNB could look like in your specific area. And, for $20 (a month) you can get really, really specific data on the past and current performance of the short-term rentals in your area.
Seth is right, you definitely want to check county zoning. That's basically what I've been working through (and financing a tiny home). The good news is, you can get a tiny home that is a certified RV and along with that comes easier financing.