- Minimum period contract term or agreement?

Three people signed the rental agreement, which states all tenants are joint and severally liable.

Consistent reminder of paying rent, automatic charging of late fees and ability to add addendum for changes in lease agreements.

If you do go the LLC route I would pay more attention to the LLC Operating Agreement than the concept of an LLC.  

If the approximate $140k is seller financing, are the terms of such agreement made in the real estate contract? 

If your lease contract is much more thorough and comprehensive than the lease they're on now, you may want to try having the current residents sign a new lease using your contract (you would probably need a mutual termination agreement as well to void out the existing lease; again, I'm not a lawyer, so definitely worth consulting one!).

I've heard so many horror stories, and know I am bound to have some myself, but what are some things that can prevent disaster by including in your lease agreement?

Money order is an added protection for the tenant because when the payment platform is hacked and everybody’s information is stolen, the tenant’s information won’t be there and therefore cannot get stolen.Look at the agreement documents the platform forces you/tenant to sign.

You can do a lease option agreement or a first right of refusal agreement.Definitely would need to get an attorney involved for the specifics

However, if the new month to month leases change any terms of the existing oral agreement (utility switch, rent increase, etc.), the tenants will need appropriate notice of the change in terms before they can be asked to sign new leases.