Wizards automatically start with a couple (three, IIRC) and clerics automatically start with Gentle Repose and one other of their choice. So, yeah, it's intended for them to start with rituals.
Any other character trained in Arcana or Religion could start with rituals, too, but they would need to buy the Ritual book and pay the market price on the rituals from their starting 100GP. As mentioned above, this would be pretty expensive, so they'd have trouble acquiring other stuff. Maybe a warlock could afford it, as they wouldn't need to start with an implement or heavy armor. But a paladin wants to buy plate armor, a shield, a good weapon and some of the standard adventuring kit, so they won't have a lot of GP left.