Before buying a resale flat, always see to it if the Title is clear.
By clear and correct title (not a defective title) it means that if the correct stamp duty was paid earlier, the document should be properly stamped and registered.
See to it that you conduct due diligence by engaging a local lawyer.
so that the same flat is not sold twice or thrice to different people.
see the previous sale deed.
any amounts paid to the builder/society - receipts for the same.