I rent nice places to renters all the time and they take good care of the property, pay rent on time, communicate well, etc.

But if you took a HELOC, which tends to have relatively high interest rates, your blended rate (the average of what you're paying on your mortgage plus the rate on the HELOC) would likely be in the same range as today's mortgage rate.You'd also only be renting out one unit, but by selling it might allow you to get more than one additional unit and still grow your portfolio. 

So that by the end of the amortization schedule, almost the entirety of the monthly mortgage payment goes directly to pay principal.

It would just be so much easier to let B report all income/expenses than to have A & B split everything but A also pay B rent!

Insurance would cover it, I would pay the deductible, and no assets would be lost.If you are in an area like San Diego where people are more likely to sue, a judge is more likely to find you guilty, and the payout is expected to be higher, you may consider an umbrella insurance policy.

You may still want to consider opening up a separate bank account because there may still be some expenses that you pay for directly outside of what is paid by the property management company - I.E.

I could use the HELOC to finance my down payment and rehab and then when I refinance my BRRRR, I could pay off the HELOC and close the loan. 

I'm 32 years old, with a good paying w-2 with an always abundance of overtime availability.

The well serves about 74 properties (some lots are vacant)  of which currently 40 are paying and the owner estimates as many as 18 may be stealing water.

The ones that sell the fastest are the ones you want to pay attention to.