What ROI are private investors looking for on a unique flip?

[Alicia Herring]

I'm finding off-market houses that are on larger than average lots, where a lot or two can be split off and sold. Whether the original house is kept as a rental or fixed and flipped, what ROI are private investors looking for? I have a partner who is willing to go in 50/50 on profits but I'd rather find a private investor and give them a good return on their money. As I'm evaluating each deal, what ROI can I assume a private investor is looking for? I'd think 10 - 15% ? If so, how do factor in the time? It could take anywhere from a 4 months to 4 years to cash the investor out.