I understand your problems...
Going into a flying group is like a marriage, don't go in without fully thinking it through because you really can be disappointed and lose a lot of money. Be very cautious of being driven by the heart, let the final decision come from the head!
But... keeping your feet firmly on terra firma will stop you losing out in a big way and joining a good honest group will give you regular access to an aeroplane that no flying school can offer, where else can you take the aircraft for the full day and put only a couple of hours on the tacho?
Also you might meet that "flying buddy"... this is essential because the actual flying skills become less of a challenge and the adventures become more important. A like minded friend will join in stretching your respective legs and some good trips are undertaken.
Regarding the group...
Be careful of why the share has become available, is an old trouper selling up before a big bill like a replacement engine?
Check the hours on the lump (2000 before overhaul) and whether there is an engine fund.
Check the actual technical log and find out the aircraft utilisation, will they be able to fit you in? The person you are buying from will probably not be an active flyer so the others might not be used to this slot being actually used.
And finally... does the share actually exist, I do know of a Cherokee share once sold 6 time over!
Lots to tell, I am sure there are good and bad experiences out there... find out all the details and post them up here.
Go in with your eyes wide open,
Beagler (a happy group flyer)