If I was to find a property, and ask one of the investors to put up $15k and I put up the other $10k, then every quarter split the positive cash flow between us at some pre-determined percentage.

Some sellers want to wait and see what the market will yield at the end of the lease or want the option price to be $30k - $40k above the retail price today.How can you get the seller to agree upon a pre-determined option price at today's market price?

Predetermined late fees are deemed illegal and any such fee must be justified by the landlord as a real cost.

@Robert JensenThat sounds arbitrary to evaluate you a predetermined cost.  

This can also be used as a short term basis if you're flipping the property (any amount from the sell minus the predetermined price goes to you.) 

The idea is that you pay an upfront option fee (1 to 10% depending on the owners market/motivation/competition) to purchase the house later at a predetermined price while you rent it, usually at slightly higher market rents (& you may be given rent credits for monthly on time payments which will be used for your closing costs at time of purchase).  

My thought would be that I would bring a relatively small cash contribution but give most of the overall appreciation to the flipper, in exchange for the experience/knowledge that I would be earning and the promise to be the guaranteed first offer with predetermined price range when going to refi (maybe even with private hard money on family-member-terms).

More Financing options Lease-purchase agreements: A lease-purchase agreement allows the buyer to rent the property for a set period of time, during which they have the option to purchase the property at a predetermined price.

Investor buys home with pre-determined sale price to tenant-resident (ultimate home owner) with targeted purchase of 6 months to 3 years.  

Automatically add money to an S&P 500 ETF into your Roth at predetermined periods spread throughout the year to surf off both gains and losses.