Conventional cash-out refi isn't in the equation.

If they move then you would have at least one month of vacancy I would think so you have to factor that into the equation.

I am apprehensive about getting involved with family matters that focus around business matters, especially when they have six-figures in the equation but she was adamant for me assist.

In the future you will eliminate the lender/partner from the equation and just borrow the money verses have a third partner. 

That's how much three decades of social change in America made to the basic money equation: three  percent.

I equate self managed, out of state tenants to a long distance prison relationship, lol.

Even if you form your entity out of state, you will pay CA taxes if you are managing from CA, which equates to "doing business" in CA.Depending on what kinds of activities you envision doing with your group, you should speak with an attorney for the right type of entity. 

It could be useful to help inform pricing decisions for properties to be listed/bid on, as it would give a simple way to estimate the average price of a house with the characteristics you plug into the equation.

To the OP - if zoning doesnt allow it to be improved as a MHP then just take it out of the equation as a whole.

I hope this doesn't detract from your post, but I am on the other side of this same equation and have some related questions.