Wow you are willing to give an equity partner 60% of the profit? Let's run the numbers:
Example:
Buy house for 200k
Fix house over 6 months for 70k
Total cost 270k
Sell house for 400k - 30k in seller contribuitons, holding costs, RE fees, etc
NET 100K
40k to you. 60k to equity partner.
OR
Borrow 270k at 10% + 2 points
Fix house over 6 months
270k+18.9k to lender (actually call it 22k because lender will probably have extra junk fees built in)
Total cost 292k
Sell house for 400k - 30k in seller contributions, holding costs, RE fees, etc
NET 78K
78k to you.
Then there's the PIA factor of having the equity partner stop by to "check on their investment" and present their ideas on how to do things, etc.
Of course the other side is you have to be able to make the monthly payments to the lender unless you negotiate that the interest be paid in arrears (when the house sells).
Since I've got a proven track record I've got guys proposing to partner up with me all day long. I'd consider it at 20% so it works out about the same but only on larger deals.
Having a credit partner for short term flips seems to be the way to go. Equity partners for longer term deals or much larger projects. Say you are buying a fixer upper apartment complex. Sure those numbers may work but I'd shoot for receiving a percentage of the net monthly rental income as well.
If you don't know them probably best to work with them as a credit partner. Everything clearly written out and closed with attorneys. Your rights and your "partner's" rights recorded in the public records via Warranty Deeds and Security Deeds.
K.I.S.S. (Keep It Simple Silly)
Of course there are other much wiser folks than me out there that put together syndicates and the like that may have other ideas. It's certainly possible.