According to that chapter, an “outright gift of the cash investment is acceptable if the donor is” one of the following: The borrower’s relative / family memberThe borrower’s employer or labor unionA close friend who has a “clearly defined and documented interest” in the borrowerAn approved charity organizationA public entity or government agency that offers assistance to (A) first-time home buyers or (B) families with low to moderate incomeThis just handles the down payment funds.

What I have found is up to 18% rate, that's seems so high to me and that's with providing income documents and $10k down.

You might buy with a 15% discount, depends on the note, the history, the documents, the collateral and the seller's motivation.These private notes  are dealt with one on one.

Or $200/doorThe current owner has been bad about getting us documents, we have yet to see the leases, which is making me nervous, and the cost of the roof being an unknown is also worrying me.

I would like to schedule a consultation asap and do a document review. 

Document it.

You would need to consult the Denver zoning guidelines (can be found online) which is a 1000 page plus document to see if an Additional Dwelling Unit (ADU) is allowed on that property based on it's current zoning.

In Calif, we use the forms provided by the RE agent - - unless you are attempting a FSBO or wholesaling transaction in which case you are on your own for all documents. 

The seller must check their loan documents to see if a wrap loan is allowed. 

Hiring a lawyer to draft or review the document is totally up to you.