LLC Partnership Structure

[Sam G.]

Could someone point me in the right direction, if there are any previous posts that address this?

I have a project that I am working on, the formal partnership is not set-up yet. 

There will be 3 partners (each providing a portion of the required investment, and each taking a portion of ownership/profits in the LLC) who will be listed in the LLC. Other family members & friends are interested in providing cash investments to the LLC to get us started (to receive a set return, guaranteed), but will not be partners in the LLC.

What type of partnership structure is the best for this? And how are the family/friends that provide cash investments structured for the LLC?