Can you write investments into referrals off on taxes?

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So, I was thinking to myself whenever I start bringing some cash in from the PTC's i'm a part of and investing into my favorite/cheapest and most reliable PTC's. Can you write that off on your taxes? Has anyone ever tried? I mean, personally I consider that a "business expense"(not sure if that's what you would necessarily call it) so to speak since you're investing money in to hope to make a profit for your investment. I'm basically asking, is it a reasonable assumption that to some degree you could write it off & get some money back?