Would you cover the repair costs as well, or is that on your partner? Usually an equity partner covers all costs and the working partner manages and does the work.
So if you only put in the purchasing costs, and he fronts the repair costs, then the equity partners 50% of the profits is split between all equity partners (And since your contractor would be putting money into it, he is part of that group).
Example:
Purchase at $100,000. You buy
Repairs at $50,000 Partner fronts,
Resale at $300,000
After fees etc a profit of $75,000
50/50 split puts it at $37,500
Since the equity partners had a 2/3 and a 1/3 split on investments, then the contractor gets 1/3 of that $37,500.
Final numbers, $50,000 for contractor, $25,000 for you. Since you invested $100,000 over 6 months or so, your cash on cash is still 50%, and you didn't have to do any of the work, thats pretty good. If you front all the costs totaling $150,000, and get the $37,500, you would still be making the same cash on cash, so it all depends on what you want.