There are way more rules and regulations of having a building and renting out per room.

If you’re curious, look up adverse possession regulations in your state so you’ll know what kind of situation your neighbor is in.

I would check with your local municipality. guidelines first to make sure you're not violating any new regulations. 

The first floor tenants access the basement through a locked door and set of stairs.The door panel itself is not able to accept an internal device (aka like a regular exterior door) because it’s too thin.Thoughts on if removing the deadbolt and giving both tenants the keys is the best solution?

There are federal regulations that need to be met when you are handling it.

I had read in Oakland's HBX zone regulations manual for a dwelling unit there is a minimum 930 sf of lot area per unit however what happens when the lot is less than that?  

And some regulations you have to be aware of. 

Towers come with own set of rules and regulations for fire, compliance, central mechanical, elevators, roofs, accessory rooms/office, and model units- this has been amazing experience working on building new efficiencies, implementing CAPEX with large NOI drivers - VeryExciting to have walked the gauntlet on the tower apartment versus garden-style - Truly expanded knowledge and experience.

Towers come with own set of rules and regulations for fire, compliance, central mechanical, elevators, roofs, accessory rooms/office, and model units- this has been an amazing experience working on building new efficiencies, implementing CAPEX with large NOI drivers - VeryExciting to have walked the gauntlet on the tower apartment versus garden-style - Truly expanded knowledge and experience.

Thought I would share this article that covers new regulations, some of which are going into effect this week:1) Rental registration 2) Late fees 3) Security deposits https://finneylawfirm.com/2020...