My name is Geoffrey and I just signed up as BP Pro members couple weeks ago because I really want to know more about real estate investing.

On a Non-QM loan, you can finance the property in the name of the LLC but must sign a personal guarantee.

Tenants are given a bank account number at a local bank (I have one account per building, exact rent amounts are unique within each property to avoid confusion with deposits), and as a condition in my lease (which they signed), they are REQUIRED to make payments to that account. 

You can be sued by any member of the transaction based on what was said or omitted.

Can I sign a regular tenant lease with them, or do I need a roommate specific type of lease?

In most areas, yes....not traditional hard money, but a Transactional Funding Lender.....1-2 points for a same day closing.

Parental co-signing is possible but not probable.Has anyone been in a similar position?

Otherwise I usually just track down the previous owners and get them to sign Quit Claim Deeds to me.

I think @Ryan Paltridge would agree that one of the best places to find a great lender that has experience in the owner-occupied residential 2-4 unit realm (and can actually close the deal) is through an agent who has experience in the same types of transactions. 

I agree with Andrew - don't have your new tenants sign a lease until you've had some time to experience them as tenants.