Dave Bonta's short poem plays with the idea that a client is something like a deity. The first line and a half is a rapid list of verbs, the things a client does: come, buy, talk, dine, demand, agree, use, meddle. Some are pleasant, some are annoying, and the list slides from simple purchasing into interference. By the end, the client is "a little god / of trouble."
The joke is in the shift from commerce to religion. Gods are asked for things, feared, and placated, and the poem suggests clients get the same treatment. The word "little" keeps the god from being grand, so the tone stays wry rather than reverent.
The last line, "one that I believe in," is where the speaker's feeling shows. It sounds half sarcastic, half sincere. The speaker seems to put up with the trouble, perhaps because the client is what keeps the work going. The mood is dry, tired, and amused, with a bit of grudging loyalty underneath.