I always thought this was a smart idea. Lump all the single biz owners together and buy coverage as a mega-group. That makes way too much sense to be considered...
It's not possible... You have to be a business, non-profit, etc... You can't just be a bunch of random people. Even if you found a group, you'd need to put together some legal structure to make it work.
If you're starting your own company, the last thing you want to worry about is starting another entity, finding a group and buying healthcare--you won't have time for real work.