A double-entry system (like QuickBooks) allows you to reconcile your bank statements, ensuring no missing or duplicate transactions.

If E has any priority over B, for instance, I would not invest in this structure, given that my bank account puts me at a Class B share (side note, their Class B is a little more GP friendly on the surface, than other groups, but devil is in the detail).  

In this manual (which I assume could be modified to provide to tenants) I include all the financing information (which you would not include for tenants) bank accounts, mortgage accounts, payment information, and mortgage payoff), a list of the contractors, what each contractor does, a list of upcoming planned or necessary repairs, and a copy of all leases associated with the property.

Banks can shut down an equity line at a whim, so there is a strong risk there.

Now purchasing a home with cash is always good b/c obviously cash is king but also I think the part you might've missed is that, the money your utilizing on these home's won't actually be yours, but the banks or whatever institution you used to fix the home or make its value worth more.

@Daniel Medellin Regarding your question, it would depend on the lender or bank you're working with if you want to go that route in the future. 

The appraiser gave the house a low score so the bank said it is a risky investment for them and gave me a 70% loan.

That is the best option if you are truly trying to help a family member.you cannot get control of the mortgage, you can do sub2 but you are not in control, the bank could call it due if they see the property transfers title.The other way is for you to buy it from them at market rate, then rent it back to them at market rate.

Would this be better to try and go through a local bank or is there good options for private money or other banks that specialize in this?

If you aren't in that club yet, do a few flips and build some bank.