You might also want to make a business plan outlining the project including goals,etc.Also take into consideration a mentor in your area.

I believe the IRS has a document that outlines what's considered capital and what's not.

DPW outlines the following MUST be submitted (verbatim):An affidavit, signed by the tenant, stating that the unit hs been voluntarily vacated.

Make sure you have a lease, outline rules, responsibilities, expectations.

Recently, a friend from church told me he was planning on buying a duplex and outlined the basic house hack to me. 

Again, just depends on where you want to invest & what your goals are, not to mention the amount of money you have to invest.Once you have that outlined & defined it will help you decide on the area. 

How do I make sure the lease outlines that the company is responsible for BOTH the financial rent payments but also the damages to the house?

The title company will draft up a promissory note and outline all the terms you two agreed to. 

But two guests ago didn't read my Welcome Guide (I know because Touchstay shows me the number of openings) then immediately texted me angry (mind you, after I let her check in 5 hours early) complaining of the pool rules, which were clearly outlined in the guide.  

Have your legal JV outlining duties, responsibilities and % ownership in place.