Sohna first-time buyer: Hidden costs aur site visit ke tips?

Sohna mein property dekh raha hoon, Sidhartha Group ke projects Sector 82 mein ache lag rahe hain. Hidden costs ko lekar thoda nervous hoon. Stamp duty, registration ke alawa aur kya budget karna padta hai? First-time buyer hoon, so site visit checklist mein kya important points hote hain jo builder nahi batate? Apne experiences share karein please.