Hidden costs first-time buyers often miss in Noida

I'm looking to upgrade to a 3BHK in Noida, maybe around Sector 149. Kids' school admission is my wife's priority, so it needs to be a safe neighbourhood. Honestly not sure if I should go for under-construction or ready-to-move. Has anyone had experience with Assotech Limited projects? Their construction-linked plan looks tempting, but I'm worried about hidden charges later on. Is it worth the risk for a lower initial EMI? Plus, what about rental yield? Are the advertised numbers actually achievable in that area, or are they just trying to lure buyers? Should I just stick to ready-to-move even if it means a bigger loan?