In some estate in the West such as CA, WA, there are specific rules and overall, it is allowed to rent out a guesthouse (or ADU - Accessory Dwelling Units).

I'd start with a place where I could live in one unit and rent the other-not a duplex, but a house with a suite or accessory unit. 

They're one of the biggest leaders of accessory dwelling units here in Denver.

Under the long-existing Denver STR rules, if your carriage house is truly an accessory dwelling unit, and was either permitted under current Denver zoning codes, or was grandfathered because it was built prior to current zoning ordinances, then you are totally allowed to do Airbnb and short-term rentals in it.

Detached Accessory Dwelling Unit. 

What's the difference between an attached accessory dwelling unit and any other space of a single-residence house?

I usually give a useful kitchen bowl filled with a few kitchen accessories and a welcome letter explaining the property rules and a list of helpful phone numbers etc. 

My current city allows IADUs or internal accessory dwelling unit.

They came out with a rebuttal says “a storage container can be used in a commercial zone because it classified as an accessory use for that given commercial business.

Important to have a cash reserve set aside so you can covet these expenses.