I have been had zero success trying to find the answer — the media seems curiously incurious.
Who effectively PAID FOR THE MURDER WEAPONS (knife, car, 3 handguns+ammo), by financing this layabout, without keeping him under control. Would that be his Daddy? Did Elliot buy the guns with cash? If on credit or debit cards, who paid the bills?
According to his lengthy autobiography/manifesto, he set aside money that his parents sent him until he had enough for the attack (~$5000).