Although the forum input can be helpful, you need to have proper legal precautions in place rather than opinion.

I don't know your state but I suspect you would be breaking some law, as you are likely unable to legally market something you don't own or have use and possession rights.

Security deposit amountYou can find plenty of examples by searching for "tenant estoppel certificate doc" or exchanging "doc" with "pdf" for more options.Here is an example and explanation: Sample EstoppelSome have a lot of legal jargon but this document does not need to be so detailed.

I could only imagine the legal agremeents needed on who has what right/easements etc.

But I can't seem to find any information about what are legal requirements for owners and property managers.

Real estate agents can’t offer legal advice, and at least in Ohio, they can’t alter the boilerplate form.

Also, if the triple is a legal multifamily, you will be able to use the other 2 vacant units at gross rent of 75% to lower your monthly mtg payment.

Are both parties represented by legal counsel?

Knowing this information will help you identify the right professionals to bring on board.At minimum, your team team should include:Financial Advisor: to help with investment strategies - portfolio diversification and risk management.Real Estate Agent/Broker: to help with property acquisition and market analysis.Accountant or Tax Advisor: to help manage financial records, tax planning, and optimization.Attorney: to provide legal counsel for contracts, agreements, and investment structures.Mentor or Coach: to offer guidance, insights, and industry knowledge.Networking and Relationship Builder (for everything else you will need): to connect you with potential partners and collaborators.

Consult an attorney and tax advisor to structure the arrangement legally and effectively.This post does not create a CPA-Client relationship.