Need opinion for buying flat

I'm planning to buy a 2bhk flat near aaradhna nagar kharbi ring road. Pros: It's a 3 apartment building, My sister already owns one. And if we buy 2nd we will have monopoly plus we are also planning to buy 3rd one in future. Cons: It's 12 year old construction. Build up area is of around 750sqft. Asking price is 40 lakh, while market values stays at 35 lakh considering it's old as per my opinion. Thanks in advances