I know the situation to which you refer at MF. The advertisement as you say talks of selling shares in a Cessna, a Partenavia and a Jet Ranger helicopter. My understanding is the club intends to keep one aircraft for training.
On the subject of buying shares there are all kinds of questions in this instance.
1. Will the clup retain shares?
2. Is the club looking to create groups which will buy the aircraft?
3. Who will carry out mainteance.
4. Where will they be hangered
etc. etc
At the end of the day I'm not sure the interest exists on the Island for a share scheme.
From your point of view as a student, I would just carry on training.
If your real question is what is the future of the club if it only keeps one aircraft, then that's another topic, but don't be afraid to talk to the owner and ask the hard questions. MF has had its ups and downs, but always seems to keep going.