GST On Landowners share of Flats under Joint Development Agreement

I have made an agreement with the builder on 20.08.2020 to develop my property (of 3800sq.ft. ground)in a joint venture.Builder agreed to offer me 50/50 basis for  building  the flats. Totally he is building  8 flats out of that he has to give me 4 flats on the arrangement that I have to pay the GST for the 4 flats which he is offering to  me. He has to complete the  building within 18 months time in all respects  and he has to pay the rent for the house for my stay during  that period. 

 

Now, he is nearing completion. Please help me what is the GST admissible for me to pay to the builder.

 

Regards,

 

T.NANDAGOPAL,