Newbie Picking a Partner

[Spencer Goldenberg]

I have a family friend who manages large multi-family construction projects. He just helped me fix up my new (personal) home. He has a ton of experience in contracting/construction. This is an area I am weak in. I would like to partner with him: having him oversee construction responsibilities because I am targeting value-add properties. However, besides the renovation, I would take over all other responsibilities (as in getting the deal under contract, asset management, financing, etc...). What would be a fair percentage of the deal to offer him in this scenario? My initial thought is around 15%. 

Would love any suggestions. Thank you!