Karkat is kinda the deadbeat of the group financially. The money John gets from his dad pretty much could cover everyone’s rent honestly? Karkat is the one that actually handles the bills and and makes sure everything’s clean, so his lack of actual cash is compensated for.
He works graveyard shifts (where he tries to memorize lines) and doesn’t come home until ungodly hour from various convenient stores. He lives off caffeine and willpower. Not many people come in but the ones that do are generally weirdos.
Which is how he meets Gamzee and Sollux.