Under-construction property hidden costs are a scam.

Been looking for a flat in Hyderabad for almost a year now, aur honestly, prices toh just keep climbing. I'm checking out projects in areas like Karmanghat, Salarpuria Sattva ke bhi kuch options dekhe hain. Under-construction ka risk factor kya hai, samajh nahi aa raha. Bahut log bolte hain ki delivery delay hoti hai, but new launch mein payment plan better mil jaata hai, right? Aur yeh hidden costs ka kya scene hai? Builder quote karta hai kuch, but then registration, stamp duty, interiors, electricity connection... kitna extra lag jaata hai? My budget is tight, so I need to know kitna buffer rakhna padega. Jab site visit pe jaate hain, kya kya cheezein check karni chahiye jo builders usually nahi batate? Koi experience share karo please, especially first-time buyers. Kaafi confused hoon.