Agent Melanie Mills asks for 350 dollars upfront fee if she likes your manuscript.
She has gotten deals with major publishers, but these deals have been 'microscopic'.
She does not advertise that she asks for a fee in Publishers Lunch, where she has a page. She does mention this on her website, but in a vague manner.
According to her, the money is for editing services and query letters. According to me, she should make it clear on both her web pages she charges such a fee. When you photocopy your chapters and send them to her, you're already out a lot of money.