TNB application is compulsory in order to handover the unit to the owner.

Usually developer will pay the TNB and SYABAS utilities deposit on behalf of owner, then claim back from owner during Vacant Possession (VP)/ Handover keys.

By the way, if you sell immediately after getting keys, mostly will have Real Property Gains Tax (RPGT) incur. Some where around 15%-30%.

Don't forget the interest paid during construction, lawyer fees, agents fees etc... so better think what is the ideal price you want to sell, and margin