I would look at a 6%, you have a 60 year old multi unit on Susquehanna next to public housing, yeah, I want 12%.Cash on cash is a better metric just on the fact that you can also compare this to how the stock market is doing and other investment (non-real estate) will do. 

The operating agreement should address possible arrangements, how you admit another member, events of withdrawal, voting rights (might think in terms of a corporation with preferred and common stock as to voting rights), buy-sell arrangements and authorizations granted to members or managers.A good attorney isn't just a lawyer they are also planners that can map out the direction of operations, they can be the gatekeeper that allows flexibility but keeping you on the main track. 

I got tired of watching my stocks grow slowly and decided I trust myself with my money more than I trust the stock market.

Or you could rent it out after repairing if the mortgage principle was extremely low. 

I went to a similar stock options trading seminar once where they showed you all the ways you could make $20k in a day by trading options.

If the stock market had performed the way it did in 2014 with an 11% return, it would have been really crappy for the investor that funded the project.So I got lucky you say?

Definitely don't sell them to invest in the stock market!

@Nicholas Mahon As far as I know FHA does not have a 40 yr mortgage.While the 40 yr mortgage might better your cash flow, you are paying a lot more in interest and increase the risk, as it will be a long while before you truly start paying off the principle.

I think the stock market is much more at risk than the housing market.

I could really fix it for her but it is a matter of principle.