I have received an email from a researcher, who work on topics related to my field of research. The researcher asked if I'm interested in collaboration, and then explained that they have an almost ready-to-submit paper and they need funding (fees for Open Access journals). I'm assuming what this person means is that if I just provide the funding, then my name automatically goes on the paper!! I consider this to be unethical, even if I can add something to the paper.
I was wondering, is this common? Is it ethical?