you need to realize that you are not only risking your own freedom but theirs by growing in their house. If you really think its a good idea to do this, go spend just one night outside. Now realize that when they figure out you lied to them and it is weed, they are going to kick your ass out and that is where you are going to be living. You are still living the good life at home with your parents, is it really worth it to lose it all over a plant?
If i was to take what i pay for my mortgage, electricity, water, trash, sewer, cable, food etc, i could buy way way way more weed than i could smoke. Thats the way you should look at it, right now you are broke with a place to live, beats the hell out of being broke and homeless.
Good luck but realize your parents don't have to put up with you anymore, your 19!