Need advice, partnering vs. investor to purchase tri-plex?

[Emily Refi]

I am about to put in an offer on a tri-plex for short term rentals. I have a contractor who might be interested in investing or partnering in some capacity... contributing 20k toward the down payment and about 25k in repairs for a total of 45k upfront. Assumption is that I carry the mortgage, 595k and also pay about 80k for the rest of the down payment, FF&E and interior updates. 

The options are A) treat the contribution as a loan, with 8% interest, or B) Profit sharing of a certain percent, or C) We partner up with weighted shares... like 20/80 with the understanding that he will provide ongoing maintenance. 

Are there other options, what has worked well for others? And what kind of contract would you use to solidify? I have done a couple of deals, but this would be my first with an outside investor / partner. Thanks!