Can i transfer flat after society formation?

Hello all, I m planning to buy 2bhk(810sq ft) flat direct from owner in mira road,bhayander mumbai. Its an ready to move new construction, just 4 months before owner got the possession from builder. Now i m planning to buy directly from owner on full downpayment but builder is asking for rs750/sq transfer charges which is very high aprox 6lac+ going for 810 area. So my concern is, as i m dealing is full downpayment can i buy the flat in current date by only doing stamp duty & registration on my name and wait for society formation????? Bcoz society only charges 25k to 50k for transfer . If yes,then please list down all the necessary documents i need to obtain from owner at the time of deal so that in future independently i can submit all the necessary documents to society for transfer without builder/owner documentation/permission. If possible also guide me how to start and complete deal with owner and As its my first property i m confused and bit nervous too. I hope my concern was clear and i will get quality reply soon :)