I never tried anything like that. But I've been part of some talks related to money issues here, and opinions seems to range from "not much of a chance" to "don't waste your time with that".
Of course, one can make some extra money here and there (e.g., some award, some teaching). But your plan should be based on what you have been offered. You certainly is not the first PhD student on a tight budget (more than usual) because you have an international SO who can't work.
But things may be different from school to school, I don't know.