Rather than using a percentage I would again recommend you talk to a property manager or local investors and ask them what they budget for annual per unit expenses.  

If you are buying this as a primary residence, then you might be able to buy it using a conventional residential mortgage, 30 yr fixed.

If it is a single family home you may be able to get as much as an 85% LTV using a traditional mortgage which will have favorable rates and terms than attaching a second to tap equity for the other deals.  

@Colby Zeller- if you end up buying a MF proeprty - the  FHA loan is likely the  way to go ,,,,if you end up buying a SFR - using a conventional loan is likely the way to go ....all lenders  will look at   credit ...verfiable income / employment /   assets  .....debt/ income ratios  needs to be  under 49% in many cases ...

5% down payment using a local credit union How did you add value to the deal?

Consider using a MTM agreement in the future.5. 

Long story short, I've been using a line of credit ($300k @ 5%) and have completed several flips so far this year.

If you are leveraging the cash value of a life insurance policy for syndications, you really shouldn't be using a policy loan.

It may take a little time using a free app, but it's worth it.

Since you are not using a traditional lender; you can tell the private lender what you propose and then negotiate out the details.