Newbie-type question about power supply at home

To add a 30 or 50 amps hookup you will need to add a breaker, appropriately sized wire and receptical.

The cost difference between 30 & 50amp should not be that much.

If you need one roof air then a 30 amps should be adequate. If you need two roof airs or have other large loads you want to look at going with the 50 amp.