If you don't have such a clause, add it.

In addition, adding an ADU is a lot of work.

If you are the sole heir of a rehab property, usually the smartest move if you aren't experienced is to sell it for max value, as-is, and the repurpose that money into better, rent-ready homes somewhere else, possibly closer to you. 

By the way, the tenant should be charged for this as part of "cleaning and repairs." 

Let me know if I can be of assistance. 

Live in one unit and update it while you rent the other unit, then once that is vacant, move into that one and repeat.With renos, don't go overboard especially if it is a rental. 

Quote from @Devin James: Just as important: be a giver, not just a taker.

What made you interested in investing in this type of deal?

I suggest you look for clarity on what resources you can use or companies can assist in using a small piece of that equity as a downpayment on another high-quality asset like the one you already own.

They can depend on the person and the property along with a multitude of other factors.