It has been discussed before but if you decide to go into a Group in my experience the key issues are:
1. Is the Group properly funded? In other words is there an engine and prop. fund because if not you can bet both will need a major overhaul just after you join. Is the fund sufficient to cover the cost?
2. Are parts available for the aircraft? For some aircraft parts are difficult to obtain and can be very expensive.
3. What is availability like? Does everyone want to use the aircraft at weekends and does this suite you or not?
4. Is the Group well run - occasional meetings, accounts, solid training and currency requirements.
If you decide to buy, do not underestimate the costs. The operational costs often quickly exceed the capital outlay. Consider also how much you will use the aircraft. Aircraft engines in particular like to be used. You may well find for example a small Group of no more than six people gives you just about all the use you could possibly want and yet the costs are split up to six ways.