A. Don't get confused, once you entered into the Sale Agreement, you are eligible to have advance amount, then you have to give one set xerox copies to the purchaser for title verification.
B. Secondly, after the scrutiny of the xerox copies, you have to submit original verification for theirs counsel if he wishes. After the original verifications, you have to get back the original documents for your safe custody
C. Thirdly, you have to produce all the original documents in respect of your property at the time of registration of Sale Deed i.e, once you received the total consideration amount and at the time of Registration.