Although members of the petite bourgeoisie can buy the labor of others, they typically work alongside their employees, unlike the haute bourgeoisie.
Essentially they are small business owners who employ a few people. Although an owner of a small shop with a few employees does not exclusively sell their labor power for survival, they also do not really own the means of production. As a class they usually identify with the higher bourgeoisie class, but they are not playing on the same level field.