Any advice for a group of friends who want to start investing in a group or entity?

I have a small group of friends with a wide range of expertise interested in forming some sort of investment group or entity. This group includes friends that want to keep their day job as an investment broker, ER doctor, accountant, fundraiser, political consultant, IT consultant, land developer, multi-family housing builder, restaurant owner, and a dentist. We're not sure what kind of business opportunity would be most beneficial for our situation--venture capital, consulting, investment banking or maybe something else.

What advice do you have for our group?