I bought a share in a freehold on a property I owned and it took nearly a year and that was with only 2 parties buying a 50% share. So be prepared, with 6 or more I can imagine it would take a long time. In my case we had one solicitor acting on both our behalfs but some of the other tenants may want to use their own which would cause further delays.
As for your point, you may have some rights if he is not fulfilling his obligations as a landlord, but I can't see how you can force him to sell the freehold if he is not willing.
The best thing to do would be to see a solicitor. However please make sure they have experience in doing this as its not that common. We changed solcitors as the first one didn't have a clue!