@Mike Cachat, you can run all the scenarios you want, BUT if you give any percentage of the rent to the tenant as equity, you will find yourself in deep do-do when things go bad.  

I did go pretty deep into some emotional and pain and suffering issues from my past that made me who I am today, so I hope that stuff resonates with others out there and provides some inspiration that nothing can hold you back! 

Do some research on the rent - deep research.

I have always appreciated what you call the  Deep Service approach.

Deep discount - fix and flipper2.

I would be putting a $100 profit into my emergency fund so that I don't have to dip so deep into my personal funds when repairs/maintenance come up.   

But in return for an annual interest rate they are 'relieving' their business partner of any obligation to pay them the remainder of their 'profit' from the investment venture.

Start thinking about EITHER delegating all that self-managed stuff, OR start thinking about really going deep on doing short-term rental property management.

I would use your access to the MLS and deep search past Multi Unit sales back 20 to 30 years and approach them to see if you can work out owner financing to purchase if they are ready to sell.

I used to use excel but I got way too deep and nerdy with the numbers.