ADU's are limited to a maximum of 850-1100 square feet, depending on lot size. Despite their small size, they are freestanding, fully functional homes that share many of the same features and amenities as a larger home. A full size ADU typically costs $300,000 or more to build.

There are a variety of financing options for ADU's, typically via a home improvement loan or HELOC (Home Equity Line of Credit) through a local bank or credit union. This can also include remodeling some or all of the existing home.