Taxes and Investing

[verneer]

(I hope I'm posting this to the right forum. I tried to find one dealing with taxes/legal issues but couldn't find it. Please move it and educate me if necessary.)

If FTP sends me a check, and I cash it for whatever purpose, is that that income? What if I use it to play in Vegas? When does my "roll" become income? When I spend it on non-poker related things?

So ... if I take a couple grand out and invest it, does it become income as soon as I invest it?