John
I couldn't agree more regarding what you are saying about a good contractor is worth his/her weight in gold!!
However, for an equity participation into the deal, especially one of a 50/50 split, there is no substitute for "skin in the game."
A good quality contractor can still make a good bid on the rehab and still provide a quality service for that bid. I also do believe in rewarding my team, and work in bonuses for coming under budget and for better timeframes.
The contractor is already building a spread into his bid. The 50/50 split without additional benefit is just license to double dip.
@Ashley Wolfe especially at the beginning, if you don't want to be taken advantage of, you need to be OVERLY involved in the process. You need to study up on construction costs, you need to be a part of the buying process, you need to become an expert in pricing material, labor, timeframes, etc.
My true recommendation is that you do partner up with an experienced Rehabber on your first deal. It could be an investor contractor like @John Ellis or an experienced investor like @Jay Hinrichs who knows how to manage contractors. But either way, become an expert by leaning on their experience before you do it yourself. You'll save yourself a lot of heart ache!!