They pretty much all do it, some with predatory lending type practices on this board. 

The main downside is the loan limits for a house with ADU match a single family, not those of a duplex (which is higher).Rent control applies to MF where unit is older than 15 years old.  

In practicality, your lease is saying that you have the legal right to charge the rent up until you find a new tenant because you have a legal obligation to mitigate your losses.

It started snowballing out of control and that was if the ADU was permittable in the first place.

You'll have to put a tad more money into the deal or have them control 100% of the renovation, but don't let that stop you from reaching out to get financing.

The drawback I have is that it is difficult to pounce on properties that are still selling relatively quickly with the commitments I have  to my patients in my dental practice.  

Big brokerages control the market. 

Interested to see others experience as I know price ranges and rehab budgets control quite a bit of this.

You, the investor, pay capital contribution to gain control of property, and reinvestments.

I know for most this isn't practical, but for the one's that can do it-- do it.