By the time of A New Hope, Obi-Wan lives out in a remote hut by himself, doesn't seem to have any method of transportation to get into town (presumably his Eopie from RotS is gone at this point), and he doesn't seem to have much money, or it would have factored into his negotiation with Han Solo to get to Alderaan. Does any canon (or Legends) source explain how he comes by food and/or money?
The extended conversation between Kenobi and Solo in the Star Wars Radio Play (previously considered canon except where it conflicts with the films) strongly suggests that Kenobi has subsisted on hunting and barter. His cave also contains a "compact repair station" so he may be doing odd jobs for the locals:
Solo : So money's trifling, huh? Well just you try getting along without any!
Kenobi : Oh, but I do. Have you ever seen a credit come into, or leave my hand? I haven't had any, and haven't missed it in, oh quite some years now. And wanted for nothing.
The Inside the Worlds of Star Wars Trilogy factbook contains a couple of tidbits about his day-to-day existence, again, primarily (but not exclusively) based on barter and goodwill.
Ben Kenobi's simple house consists of one main room in which he lives and sleeps. He uses the natural cellar for food and water storage, and constructs mechanical items, for trading with Jawas, on a workbench.
Obi-Wan sees few beings other than Jawas, from whom he obtains foodstuffs and spare parts—though his reputation as a wizard causes many Jawas. and even a few Sand People, to avoid him. There are some who — out of fear — present Old Ben with gifts intended to appease him.
Accodring to Legends canon (2013 "Kenobi" book by Miller),
He DOES have his Eopie, Rooh. Matter of fact, it's a she and she had a baby. That is his transportation (though he also bums rides off of assorted female groupies).
He has some funds with which to make purchases at the Oasis (food, supplies) - presumably, emergency Jedi stash or something, though it is never elaborated on. He used Republic credits:
He shuffled on his feet and reached in his pocket. “Are, uh, Republic credits still good here?”
“As good as they ever were,” she said, stepping behind the counter. “We don’t pay politics much mind. Let me deal with the loose things first, and then we’ll get to what’s in the tub.” She began adding the items to his already lengthy sales tab—and as she did, she could see him counting along, keeping a running tally to himself. It wasn’t the nervous watchfulness of her more strapped customers, but he was still keeping track. So he can afford all this, she thought. But money still matters.
It's heavily implied that he will at some point might get involved with Tusken Raiders - if/when that happens, being part of the tribe would provide means to live on.