Most well run groups will charge themselves a couple of quid extra per flying hour to build up an emergency fund.Worth asking this when considering joining a group.Also ask how much spare they have in the kitty.Most small mishaps can be covered by this fund if it is big enough,but if something major such as complete engine replacement is needed (V.unlikely I would have thought) then its a case of hands in pockets for £500 quid each for a reconditioned engine.If you own it on your own,you have the same chance of needing an engine replacement and the prospect of finding a HUGE sum of cash on your own.
Most of the maintenance is taken care of the £30 a month standing charge we put into the group,and any left over goes into the emergency fund.Like I say,try to find a well-run group (unfortunately we are in the North)but really there are LOADS of cheap shares available advertised in flying mags and even more on the flying club notice boards.
If,however,you DO choose to buy outright,I would certainly consider a PFA type rather than a CofA type.Much cheaper.
Best of luck
El Cid