Thank you for your consideration. 

Helps with your debt to income, better opportunities at cash flow, and typically requires less down to purchase.In regards to challenges, I usually build in an extra 10-15% to deal with things that I can't see behind the walls, including dry rot, electrical or plumbing issues, etc.

Prices are still considerably higher than just a few years ago.

Mostly people with minimal RE experience are adding a single ADU and they often make that choice based on cash flow without taking into account the negative equity position.  

I have written about it before in long past. 2) Yes, no PM and no tenant placement fee consideration.

Ask the builder or their legal representative for a copy of the CC&Rs (Covenants, Conditions, and Restrictions) or any supplemental documents specific to the development.Financing Considerations: If you’re financing the property, some loan types have limitations on renting out a home within the first year.

Do you need cash flow from it for income or will light to no cash flow work if you can groundswell appreciation on a good asset?

That said, I do this with a a few investors on rentals since I'm a Realtor and Property Manager where I am boots on the ground for purchase, rehab and lease-up, however we had a strong professional experience/life together before partnering.Lending will also be a consideration as most lenders are hesitant to lend to non-citizens given the foreclosure challenges it can pose.

Are there any additional considerations?

So, if your current rent roll is still on the lower side, it could limit the amount you can borrow right now.However, if you have even a partial track record showing improvements.. say a few of the units are already updated and attracting higher rents.. a lender might take that into consideration when underwriting.