When buying a MHADA resale flat, it's crucial to gather specific documents to ensure a secure transaction. Key items include the seller's mother deed and sale deed, a No Objection Certificate (NOC) from the society, and an Encumbrance Certificate (EC) for 30 years. You should also request the approved building plan and check for any pending dues or liabilities. Consulting a local lawyer and conducting personal verification of these documents is highly recommended to safeguard your interests.