Partnering with an owner instead of buying outright?

[Erik Granum]

I'm considering buying a mixed-use, multi-family building in Hampton Roads, VA. The building is vacant and in disrepair. The current owner can't afford the renovations that would necessary to make the building marketable, however, he's interested in maintaining an ownership stake. I'm amenable to partnering with him -- given that he agrees to be a passive equity holder -- but I don't have any precedents to draw from in structuring a partnership.

Assuming the building is worth 100k (which the seller owns outright) and requires 200k in renovations (which I would pay for in cash and then reclaim by refinancing the finished building), what would the terms of a good partnership agreement look like?