If you don’t charge for your spiritual services, you will have to “slave away at a desk job” as you say. How does that serve the greater good?
This is not a binary choice. You could also, for example, start seeing your job as "slaving away". You could make a real difference for your coworkers and customers by being friendly, by really listening, by just being that person that smiles at them and treats them as a real human being. You could be the catalyst for change that completely changes company culture, or at least your direct colleagues. Never underestimate the value ordinary people in ordinary jobs can have for other people.