But I’d’ also ask if the girlfriend is a legal US citizen?

Just to add to what has been said here - if the seller described this as a triplex on the sale documents, they might have a legal liability.  

You will want to consult with a lawyer.In regards to your last two questions here's some background on what makes a contract valid and enforceable:Offer: A promise to do or not do something within a certain time period Acceptance: A clear and direct statement that all terms and responsibilities are accepted Consideration: A legal and adequate inducement given in exchange for the promise Capacity: The parties to the contract must have the legal capacity and competency to contract Awareness: A party must be aware of the contract Legality: The contract must be legal in the jurisdiction it will be operating in***Not legal advice*** Steps I would take: -Review contract in detail to understand each counterparties responsibilities (if you are not aware)- Email a copy of the lease to each of the tenants listed on the lease and reiterate lease expectations for termination notice, rent payment etc. - If the lease was signed via Docusign (other esign may have same ability) - you can go to the envelope, go to history and view the IP addresses for each action taken.

Highlighting features like “walking distance to top-rated schools” helped me attract renters even during slower months.Negotiate SmartlyWhile sticking to your legal rights is important, a pragmatic approach could save time and hassle.

Stop hanging out with your deadbeat buddies who spend all day drinking, talking sports, and otherwise wasting away.

This is why so many people earn large sums of money quickly (lottery, sports, entertainment, etc.) and end up broke.Take Dave Ramsey's Financial Peace University.

@Zach HowardThere is no legal requirement for landlords to actually witness lease violations firsthand.

Now this is with an uncontested legal action..

What legal requirements should I be aware of?

Any legal issues I should be aware of in this situation?