dunno about the tax thing and i'm not a financial advisor, but you don't want to tie your trading activities into your mortgage. banks are cold and have some contract made failsafe way to fk you out of everything if you make a mistake. i would be pretty safe to say that everyone on this forum has taken a beating on the market at some stage, and some prominent posters have also had some massive losses on their path to success.
seriously, if you don't know what you are doing, stay out of the market and make sure as hell it doesn't have ANYTHING AT ALL EVER WHATSOEVER to do with your house.
that aside, trading is an awesome way to make money but you have to approach it like a job and study it and learn it and be in a position to take that massive financial beating (or two) that will give you the right mindset. there are so many different methods and strategies if you just blunder in, especially with the market as it is now (volatile as hell), you'll lose your money, put your house on the line and stress your life out. this will obviously suck.
imho best bet is to papertrade stocks or currencies or commodities or whatever floats your boat while you save money to put into an trading account. then you have minimised your risk before you even start, and by then you'll know that managing risk is rule #1 (and the one hardest learnt)