It depends on what you need from them.
I usually like to define investments in such a way that there isn't someone trying to dictate how the business is run.
That's what happens when you get a partner. They own part of the business and you have to listen to them.
It takes real maturity and organization to make a true partnership work.
If you just need an employee and maybe some of their money as an investment, then you should structure things differently.
I suggest my book, Invest Local, which is full of non-equity ways to structure investments in local small businesses.
Cheers
www.DavidCBarnett.com