It’s already as modern as it gets, it can’t appreciate that much from $20 million, and how is going to rent out a mansion for $100,000 when you can buy a condo for that price?

With some of the stuff said on this site and some of the opinions combined with the litigation happy society we live in I am pretty sure someday a BP post will end up in front of a Judge.

Furthermore, if the #s make sense, combining the buildings can work wonders in cutting your overall expenses. 

If the interest you're paying your father or someone else, combined with the interest on the mortgage, combined with the principal paydown, the rent received, the expenses... if everything results in cash flow that meets your goals, then it will all come down to mustering the faith to take that next step.I would highly recommend connecting with someone locally who has house hacked... pick their brain, learn how they made it work, etc. 

The best option I could think of for her would be a 203K FHA loan, but I'm worried that the combined costs of the principal, interest, taxes, property insurance, mortgage insurance, plus the repair costs and even potential HOA/Condo fees would be a lot more than she could handle.

The other one is a duplex that is $100,000 and rent is a combined $1100/mo but those numbers only become a 12% cash on cash return if I can buy it at $80,000 which simply won't happen.  

 I suggest combining them. 

So some quick numbers:-Reno cost $8200 (i did most of the labor)-combined income 50k (w2 married 2 kids)-sell price est. 100k (comps between 100-115k) and 100k is me being generous because most of the comps are not renovated. 

Just that the market combined with your state of mind tells me clean break.You can sell all as a package and 1031 into a passive investment and collect your 7% - 8% for the next 20 years but its too small for a big group without a  huge hair cut. 

Same models apply to individual investors...they usually do one or the other, or some combination of them.Turnkey providers are flippers.