Sunder Homes ka actual construction quality sirf site visit pe hi pata chalta hai

I'm checking out a 2BHK in Sector 1B. What should I specifically look for during the site visit beyond just the flat layout? Like water pressure, common area maintenance, parking access, connectivity from Sector 1B, etc. Also, property price ke upar kitna extra budget for stamp duty, registration, and interiors? My parents keep saying hidden costs are a trap. Log 15-20% bolte hain, is that realistic for Gurgaon? Any tips, please share.