Private money lending for a rental property

[Roberto A Urquiza]

Good morning ladies and gentleman, 

My brother and I are new to the biggerpockets world, and we're glad to be here. 

I have a quick question. In the instance that someone uses private money to fund the down payment on a multi-family property, how would the private money lender get their return on investment? Do you allocate a certain percentage of the cash flow from rent towards paying them back? Hope to hear back from you guys. Thank you!