Is it rude or insulting to refuse payment for helping friends?

I do odd jobs for my older neighbors and they always offer me 20 or 30 dollars but I will refuse it, their my friends. Eventually, I take it, because they insist but I always feel guilty but at the same time, I think they might feel guilty and/or insulted if I don't take it. I few times I completed the job and just left lol but they would come over to pay me! I'm just wondering what your thoughts are.

Updates
4 mo
I'll ask another way! AI fucked my question up! If we were friends and I did a small job or favor for you, would you feel insulted if I didn't take money from you, if you offered it?
Is it rude or insulting to refuse payment for helping friends?
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