Interested in a property in Chennai Velachery

Q: I am interested in a property in Chennai Velachery, which the Seller had purchased in a Bank Auction. I have few doubts.

1. Is it safe to buy such properties, could there be any legal problems in future?

2. The origianal Owner had got plan approval to build 2400 SqFt in a Plot of size 3000 SqFt but built only 1200 SqFt on the ground floor.

He did not build on the first floor, though he had approval. He defaulted on the Bank loan and the property was auctioned with 1200 SqFt building mentioned in the Sale Deed.

This person who purchased the property built the first floor without any fresh approval. There are separate Property Tax and EB connections and cards for both the properties.

Now if I buy the property what should I do to avoid Corporation's action or to create value or to get loan against the property? Kindly advise.