I would consult an expert before doing anything.  

We loved living there so much, and saw such a huge potential in Tulum's happening real estate that we opened our own boutique real estate/ architectural studio, Riviera Maya Property Consultants.

I have 43 properties right now that I'm wholesaling and the way I do it if the spread between the price I'm buying it for is less than $10,000, I just have the buyers sign a Consulting Fee agreement.

Lynette Hellerich, works for RE Consultants.

You might have to hire a lawyer, and/or a CPA, and/or a tax consultant to advise you on the best way to go.  

For example, I've seen contracts drawn up where an individual is acting as a "consultant" and  advising/assisting the seller who is selling their property FSBO by advertising it, where at that point I can fully see where "acting as a broker" could be the accusation. 

With regards on how to handle the tenant situation - you need to consult a lawyer.

If you're investing with friends, I would just have a very clear, in writing and signed(maybe even want to consult an attorney) agreement as to who owns what and who is responsible for what agreement.  

I currently live and work full time in Tokyo Japan for a recruitment consulting firm and have only recently started researching about real estate investment. 

When the property is sold, you get paid your profit plus your capital back and the seller gets his $160 and you give him a Release of Option.It is crucial you get the MOO recorded so the seller cannot sell the property without you getting paid.Having said the above, I am not an attorney so consult a real estate attorney licensed in your state and have him or her structure it the way that is legal in your state.Hope this helps.