The tradition of spiritual seekers accepting alms from layfolk already existed at the time of the Buddha—in fact, meeting a wandering mendicant and being impressed by his serenity was one of the experiences that inspired Siddhartha Gautama to embark on a spiritual quest.
"Depending on how we look at Buddhism, we may describe it as a religion, a science of mind, or a philosophy. We do not need to say it is one and not the others, for Buddhism embraces aspects of all three. "