Personally, I invest in projects of this sort with a very small percentage of my wealth, for precisely the reasons you state and the high degree of risk associated with rising cap rates. 

I do want to thank you for the information of splitting a percentage of the business.

If one side is smaller, then you have to figure out what percentage of the whole the rental side is and split the expense by that percentage.Another thing you might want to check into is how you track a security deposit - if you require it.

Look into how these fare during contractions, are you getting a guaranteed percentage on your money? 

Managers can be great as well but they will take a hefty percentage and they still need to be managed.  

I'm just starting to get into the rental business and I'm trying to figure out what figures I should use for estimated repairs and cap expenses as a percentage of the rent or house price.

what do you use for a calculator to analyze and where do you come up with the percentages for the different fees 

So of the small amount of people who actually step up and do some profitable wholesaling it seems a high percentage of them quit soon after from burnout. 

When I enter estimated potential rental income for the top floor (2000) and 1st floor (1700) and a garage space I can rent for storage (100) my cash-on-cash percentage is in the negative (about 11%) and monthly cashflow is -$100.00.

You have to put down a percentage up front and you make payments on the loan like a mortgage.