1) Regarding the threshold limit vis-a-vis contribution from each unit/member, please refer to Srl No. 2 and 4 of table appearing in Ministry's Circular No. 109/28/2019- GST dt. 22/07/2019;
2) 7,500/- limit is for member.......no distinction between residential or commercial unit in the Society . Kindly refer to the definition of "person" under Section 2(84)(i) and 2(84)(l) of CGST Act. Accordingly, "Society" is a "person," and when it collects from its "members" as per the prescribed monetary limit is taxable under GST Law.
As such, all Member-based Societies registered as "Society" are non-profit organisations only unless assessed under Income Tax Act for any "business profits/Commercial activity related profits."