Is it a bad idea to offer to volunteer through the training stage of a new job?

I have 0 experience anywhere and I am getting denied left, right, and center because of it. I am going to be interviewed for a position next Friday that listed 5 years experience required. I am honestly not sure how I keep getting interviews for positions I'm not qualified for but I show up and try my best. At the end of an interview I wanna tell them that I understand the cost of training a new employee is high and that I am willing to volunteer through the first three months if it helps me get my foot in the door. My brother advised me against it saying it will make you look desperate but at the end of the day they say no ill never talk to them again. Plus I am desperate, any longer and I wont be able to afford to eat.

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