Villa - GST regards

Respected Sir/Madam,

I joined as the Accountant (Manager) for the Associations, (i.e., Villas – 63 Nos), now I have few doubts in regarding to GST, now each villa is supposed to give Rs 7000/- for maintenance and Rs 300/- to Rs 1000/- towards the reimbursement of Water expenses.  Now the associations should collect the GST on maintenance and as well as water reimbursement??

Suppose only 10 villas will crosses Rs 7500/- and remaining will be below Rs 7500/-.

Now they have to collect the GST for All 63 Villas or only 10 Villas.

Thanks in advance