Besides technical details about the area, one should verify the building plan approved by Municipal Corporation or such other competent authority, commencement certificate, ownership documents (title documents) etc. If it is a resale flat then verification of further documents such as Share certificate, Rent receipts, Maintenance receipts etc. becomes necessary. Verification of Occupancy Certificate is also important wherever applicable. However, this is a professional job and the services of a competent advocate shall be used for the same.