All states and counties are different, so you need to read through the county documents carefully and consult a local real estate lawyer.Some counties will only sell the tax debt. 

I care less about the payment process and more about communication, accounting, documentation, processes, etc.

You would have ongoing filing requirements with the State and would need to keep business records and documentation.

Saying there are three people living there when only one is on the lease is good to know, but hard to prove; getting video documentation of three people consistently entering/exiting the property substantially alleviates that difficulty.During your due diligence process, you probably obtained a copy of the existing tenant's lease to review.  

Leave it to the experts is my recommendation on drafting all the documents after the terms are agreed too.

In a “nutshell”What can work - partnerships where each person brings a different necessary asset (knowledge, experience, time, capital, credit) to the table, the responsibilities, rewards, and expectations are clearly spelled out, legal documents are created to head off disagreements, and the parties are compatible.What doesn’t work - partnerships formed by two or more inexperienced people looking for “comfort” rather than going it alone, and anything other than the above. 

In practice, it can be difficult to not sign your name on some publicly recorded document, or some other document that can be gotten a hold of... 

If you have great documentation W-2 type income and you are not looking for the exact same thing that everyone else is looking (eg, a condo in a tourist area that won't allow airbnb's anyway) or a small multifamily in metro San Juan) then you may be in luck. 

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.

Regarding your question, earnest money, in my experience, has always been documented on the actual sales and purchase contract that you have with the buyer, and not on the assignment fee.