If it is viewed as a partnership arrangement it would seem to avoid the lending regulations and SEC restrictions Bill Gulley speaks of.

Are other financing arrangements common such as percent on the loan plus a cut of the profits?

From there I arrange to meet the owners and look over the property (if I can).

You call and arrange viewing... 

We could still structure it as a private lender arrangement.

Additionally, he obtained a loan to cover the remaining down payment amount that he paid to the owner, which facilitated the owner financing arrangement.

It is an arrangement that has worked for 4 year and not once has a check bounced.2 other tenants pay via Zelle,  I send the request on or around the 27th and normally get paid on that date or a day or two later.  

It looked like the arrangement wasn't working out so you parted ways.  

Forgot one more thing since I'm a licensed broker, you tell them you're not licensed, but were expecting a fee for arranging the sale of real estate you don't own?

Here are some samples of what I have done for some of my juicier fees: Working the deal for +7 months, arranged the person a place to stay (once worked a woman to the top of a list for a retirement home when she was a year wait), took them to the DMV to get valid ID or social security card from human services, contacted every relative they had for documentation for an estate, tracked an heir down in a prison in West Virginia (I was coming from Philly) to get him to sign off.