I am working with a builder/developer who is an expert at historic platted lot situations like this we are actually going to have a system that details exactly how to do these with a very robust on line app that spells it out in most all markets in the US. 

The landlord/tenant laws spell out exactly how the security deposit is handled -- usually you need to send an itemized list for any deductions and the remainder back within x days. 

I bought an agreement through eforms that I can use over and over again (I think it was $40) and it spells out all the rules, guidelines and had them sign it before they moved in.

The description of the unit in the bylaws spell our what are the common elements (owned by association), Limited common elements, and the boundaries of the unit. 

I know some people your age who are killing it.First off if you are going to partner up make sure you have a thorough agreement in writing spelling out roles, investment, profit splits etc.You will need a title company or closing attorney to close your deals.

Spell out the criteria required to occupy on your application and what happens if they fail to meet those standards.

You can ask them if they will prepare the promissory note which will spell out what the payments are and when they need to be made and any late fees.

Make sure you get a buyers agency agreement signed with your client that spells out your compensation and includes a non circumvent clause 

The reason this is a bit more complicated is that their operating agreement spells out some unique restrictions.

If your keeping it in whatever entity it’s in make sure to create an operating agreement that spells out yours and everyone else’s roles/responsibilities.