Brain injury support groups are fabulous. Finding an entity to sponsor one is important. Getting a meeting place and funds for mailing announcements/meeting dates is needed.
www.BIA.org has lists of support groups. Rehabilitation hospitals sometimes have groups or may be willing to support a group.
Our group has two sub-groups. After a presentation from someone in the rehab industry, we split into caregivers/family with a moderator and injured with a moderator. The moderators are social workers/case managers/ or various therapists.
I wish you the best at finding the support you need to start a local group. It does not need to be a complex non-profit. It can just be a not-for-profit association or LLC.
Our group is sponsored by a rehab doctor who donates his "court legal expert" fees to our group.