Seling of property- long term capital gain

Dear Members,

I am planning to sell my flat.In august, I will finish 3 years of purchase of that property.

I want to avail long term capital gain on that property.

I have a buyer, who is ready to purchase the property.We agreed to start the registration process of that property in september.

My question is : Can I atleast initiate the selling process now? 

Signing of sales agreement(Taking 10% advance from buyer).Buyer is planning to take the loan from SBI bank, using that Sales agreement.

Experts, please suggest.

Thanks in anticipation,