Dear Friend,
In your case at first you have to make confirm that what is the Govenment of Rajasthan policy for the registration of the group housing society. As I believe the societies has to be registered only when there are more than 21 members in it having individual flats.
In case you can not register the society you can go for the one agreement among the all flat owners that they will bear all common expenses at prorata basis divide among all and if that perticular flat holder do not wish to participate in that agreement though you can not enforce him to do this legally but can bycott him from the group socially and friendly both. This is only the remedy which you have as per my long experience.
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With Regards !!
Anand Bali, Adv.
(B.Com., M.A., LL.B., M.B.A.)
Supreme Court of India