Whenever a property gets sold to a buyer, a Sale Deed in their name gets registered in the concerned Sub-Registrar's office. This transaction will reflect in a document called Encumbrance Certificate which can be easily applied for in a Sub-Registrar's office. An Encumbrance certificate will only partly solve your problem as it will show the past sale transactions and mortgages if any. Since you want to be safe, you should get the entire property documents of the project verified by an experienced property lawyer. They will trace the history of the land and make you aware if their are any risks associated with the purchase. They will also verify whether the project has got all the relevant and necessary approvals from the Government bodies.