That is a seller credit/concession, along with any deposit but remember to have that money on hand as it isn't yours but it's still a credit.You'll get the prorated portion of taxes for the year.  

I've been most of the BRRR already except I've never done the Refinance portion of the plan. 

( deferred maint )your monthly portion of mortgage payment ?

We have been working with the city and sending our GC down to the city planning department to see how we can make the second unit a 2/1 and a portion of the garage a 2/1.

We want to use him for a portion of the downpayment/rehab costs and give him a return on his money, but not use him for a third borrower.

I'm most excited to learn how to do my own repairs and definitely plan on doing a good portion of the work myself - the knowledge gained from that is essential. 

I would suggest that if the rented portion covers all of the expenses that you take your income and put that towards another property.Good luck!

At the same time, they are pushing to legalize "home sharing" where the owner/occupant lets out a portion of their home to a renter, as this is something their competitors have yet to offer.

The part I would like more help understanding is the "refinance" portion.

I don't know your floorplan, but you might consider expanding into only a portion and keeping the remaining as a smaller unit.