
- A separate entrance
- A bedroom or sleeping area
- A full bathroom
- Others may also include a kitchenette or even a full kitchen, and a living room

- Attached - An ADU that is connected to the main house or part of the primary residence but is designed to be an independent living space. This unit usually has a separate entrance on the side or back of the house. Attached additions typically require less space than their freestanding counterparts and are less expensive to build.
- Detached - A detached in-law suite is often a smaller, standalone structure built on the same property as the primary residence. It offers more privacy than an attached suite so it's more desirable for a rental unit.
- Interior ADU or a converted existing space - This type of ADU is a separate unit located inside the main house. It can be an existing area that’s been converted or modified to create a separate living space, such as a basement or an attic, but may feature a separate entrance.

Home office - It could be the perfect place if you're looking to work from home or want to have a dedicated office for your small business.
Guest quarters - Suitable accommodation for out-of-town guests or relatives, so you both can have a little privacy even while staying within your property.
Residence for adult children or aging parents - Multigenerational living is on the rise due to the rising costs of homeownership. Since ADUs are flexible living spaces, it’s a great way for families to function together as a whole unit while maintaining each other’s independence and privacy. Adult children who are still establishing themselves financially can use it as a tiny home. Likewise, it can also be a permanent and practical dwelling for aging parents or relatives, especially for young families who want a home-share situation.
Rental unit - Since many ADUs can be considered as fully equipped apartments, they make ideal rentals. Renting it out for an extended period, or even for shorter terms through apps like Airbnb or VRBO, can help you recover the expense of building the unit and could potentially help you pay your mortgage.

2. Purpose
3. Utilities and infrastructure