I do not capitalize the first word of the next line unless it is the beginning of the sentence. So I agree with what your one writing friend told you. I was told several years back that capitalizing the first word of every line was an old-fashioned practice. I don't have any specific resources to confirm, but I think I was told this either by an instructor in a class I took once or a paid, professional critique.
And, just as an added thought, it's always good to try to meet "current practices" in formatting, but it really comes down to the writing. If you write a fabulous, "I must have this" piece of writing, I don't think capitalizing/not capitalizing a word in a line would change an agent/editor's mind.
I look forward to hearing others' thoughts!