Buying a 15year old flat in Ramapuram

Hello all, I'm planning to buy a 15year old flat in Chennai, It's a 4 floor building with 120 houses. The house is in good condition, and the society is also well maintained. But I'm concerned about the fact that it is a 15 year old building and I'm planning to stay here for the rest of my life. What are the factors should I check/consider or ask the seller before I buy this property. Also, would like to know if there is any pro in buying a new property which will cost 30L more for me in the same area.