After two lessons, I think that it is a bit premature to even think about buying into a group. Chances are that you will be able to buy into the group later if you wish and at that time see how the new group is running. It may all be a disaster as so many groups are - but then it may be fine as so many other groups are! The problems arise for instance when a new engine or other significant expenditure comes up and there is not enough cash in the kitty to cover the costs and one or more of the group is skint!
Get your PPL first then go for a share in an airplane if that's what you still want. A 1967 Cessna 172 isn't on my 'must buy' list I have to admit!