Convertible car seats and handles

Ju

I am a FTM so I have no idea how this works. I am looking to buy my sons car seat ( he arrives in august) but since they can get pretty expensive I am interested in a “convertible” one that can be changed as he grows so that I can make it last longer BUT every pic that I have seen there are no handles to carry him while he still an infant. Are they not meant to be mobile or is it something we have to add ourselves?