In general, positive actions (such as helping people and being generous) lead to good experiences and happiness, while negative actions (such as harming others and being deceitful) lead to bad experiences and unhappiness.
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.