I am a Ph.D student. A professor from another university is interested in hiring me part-time for a project that he just received funding for. I am interested in the work (to hone my own skills) but I have asked and he has said that a co-authorship is unlikely to come out of this. The hourly rate is a bit lower than I have been used to—would it be appropriate to ask for a higher hourly rate? I’m having trouble thinking about how I would phrase it.
I think that under the circumstances you could just state your requirements. It doesn't seem like he is offering you very much professionally so you should ask for what you want to make it attractive.
Of course, he may not be able to offer what you want, or may be unwilling to do so. But you are giving up your current position to do this and the rewards seem a bit nebulous.
Other considerations might apply, of course. Is he a superstar that can/will advance your career otherwise? Is his position on co-authorship firm?
Think about the whole package.