Tricky to give accurate figures;
Insurance will depend on pilots hours. My RV with 4 named pilots is currently approx £1200 a year with fairly experienced pilots.
Hangarage will vary wildly depending on where you keep it. Easy to find out; call the airport you have in mind. They often charge a rate based on length X span.
I'm on an LAA permit so annual & ARC fee's are unknown to me but are probably going to hit 4 figures easily. Obviously the larger the group the less these costs will hit individual pockets, but the larger the group the higher the use (potentially) and less availability, if everyone is an active member.
If you have a group of 6 to 8 members, in my opinion, you will have a good compromise of availability and affordability of running the aeroplane.