I'm leaning towards separate bank accounts to be safe.

However, not so far away, we had another investor who tried the same strategy and it failed miserably as comps with standalone ADUs were not adding value the same as in the market not so far away.Research your market, even down to the street in various neighborhoods well. 

Yes, you read that right, the American system was designed to best facilitate FAILURE not success. because when there is freedom to FAIL, it comes from consumers ability to choose, choose who is worth it, who isnt, and the poor performers fail and the good performers are rewarded. 

I just got off the phone with a law firm doing the foreclosure legal work for a bank.

SOS......I closed on my investment property last Thursday, lawyer, title co, realtors paid and keys handed over to buyer but the wire from the bank ( the title company uses) keeps getting rejected by my investment company.  

Just a little worse than a bank CD.

I then was offered a position at a local growing investment mortgage bank.

It's a friend or family member and not a business, like a person, they would need to submit a proof of funds from one bank account with a signed letter saying they will provide the funds for the purchase of this address.

The property is being sold by the bank.

If you are taking about dropping a million cash into properties each year, then yes you are going to want to have some type of reasonable corporate structure, but if you're talking about 25% down 100 grand properties with bank notes, all you really need is some decent insurance.