How much should a gardener charge?

i just started doing garden maintenance. i was wondering how much a gardener should charge in northern california. I charge by the hour, $30 for me and $17 for my helper. if your know about this business, is that too low, high, or fine. would you be willing to pay this rate, pay more or pay less? i do not want to over charge, since i want to build a good relationship with my clients, but i do not want to leave profit on the table. thanks in advance.