I have been extremely happy with the results and gotten more calls than I expected. 

Some of the drawbacks are the costs (initial licensure, yearly state and national realtor association dues, and perhaps broker expectations depending on your broker). 

If you hire a good property manager, they will take care of anything a HOA normally handles and the great thing, you can find a new PM if they aren't meeting your expectations, much easier than trying to remove a HOA board member.

A hard money lender would likely charge 8-12% interest.A home equity line of credit (HELOC) is running around 5 - 6%.If he invested his money with someone else, he would expect a fair market return on that investment.

What should I expect?  

I will also be completing my real estate schooling and expect to be the listing agent for the houses.Has anyone heard of deals like this or find this reasonable/enticing for a partner? 

If they are waiting for you to buy the house and get it rent ready- are they going to stick around if it takes longer than expected?

I'm risking it all.That said, I hate giving up the appreciation I expect to continue (with a minor slow down 2018/2019) by not buying more.

My 10 unit cash-flow only went up $1700, but it was a fat payment with a low balance (old loan) so it was messing with my DTI.  

Awesome to hear you have a path, some drive and some realistic expectations.