If you buy into a group, it is the group (and not you personally) who will pay the insurance. Their insurer will stipulate the minimum pilot requirements, which could be just a fresh PPL for a C150, or min 100 hrs P1 if it is a £200k complex retractable! You've got to meet that requirement.
Your personal life insurance is an entirely separate matter, and as you say if you have no dependents then it would be a waste of money. Normally there is no loading if you say you plan to fly less than 50hrs/year, and there are some life insurance brokers advertising in the aviation press who claim to have done special deals with some mainstream insurers and take this to about 100hrs/year.
Yes you've got to be very careful about the group you are buying into. I am an owner now but looked at several groups on the way, and all the shares for sale were those of "unwanted" members, and in every case I recall there was a long running dispute regarding maintenance. Not legal maintenance (which has to get done anyway) but repairs on stuff which is needed perhaps for IFR flight only. If you want a plane which is IFR legal, and all the other members only fly VFR, you can end up with a useless share which you then need to offload, preferably without the buyer discovering the genuine reason for you selling. A LOT of things can pack up on a plane and it will still be "VFR legal" and you might not like flying a plane that's falling apart even on nice days - I did my training in planes like that.
So... identify the sort of flying you want to do, whether you want to do any additional training, and check out the group by speaking to its members individually (personally or on the phone) and by speaking, discreetly, to the service organisation maintaining the plane to see if there are disputes re outstanding repairs. If the members are unfriendly or difficult or you get a bad feeling about it, drop the idea and look at another group.
Another way is to form a group with a few people you know. It's pretty easy. Any street corner accountant will set up a limited company with you all as shareholders/directors, and then you just go out and buy a plane
Make sure a specific person is responsible for maintenance and admin etc.