First time using OPM. Any advice?

[Charles Amble]

Simple example: I want to purchase a multi-family property for $100k and am willing to put down $10k of my money. Three other investors are each willing to invest $10k.

What percentage of ROI should I offer?
With their investment, are they a partial owner of the property, or do they just expect a percentage of their money back over time? 

Some background information: I've got a strong track record over the past 5 years with buy/hold duplexes but would like to get into something a little bigger.

Thanks in advance!!!!