Im growing in a closet at home aswell, and condsider myself pretty advanced with closet growing - if you could call closet growing advanced!
Anyway Id love to help, but youre going against your parents wishes - so sorry dude, no help from me. Id just feel guilty if they caught you growing and you got chucked out/grounded etc. At least ask them and present the facts. Tell you what, Im a nice guy so Ill help you with that. This is the short version of how I won my parents round -

I WONT DEAL IT.

I WONT GROW ANYTHING THAT RESEMBLES THE SIZE OF A TREE.

I WONT GROW ANYTHING IF IT STINKS (If it does start to stink, Ill either take it in the garden - with their permission - or throw it/give it away. Lowryder is the answer to smelly houses).

IF YOU HAVE A SUDDEN 'CHANGE OF HEART' AT ANY POINT, I WILL AGREE WITH THROWING THEM OUT.

IF THE POLICE GET INVOLVED, OR I THINK THEY GET SUSPICIOUS, I WILL STOP GROWING AND WONT GROW HERB ON YOUR PROPERTY AGAIN.

I WILL PAY FOR ALL ELECTRIC COSTS, AND I WILL BUY ALL MY OWN GROWING EQUIPMENT WITH MY OWN MONEY. IF YOU NEED COMPOST/SOIL IN THE FUTURE, I WILL REPLACE WHAT I HAVE USED.

IT SAVES ME A HELLUVA LOT OF MONEY - IT COSTS £20 FOR 3.5 GRAMS ON THE STREET, AND I CAN GROW A FEW OUNCES OF IT MYSELF AND IT WILL ONLY COST £60 IN ELECTRIC, PLUS THE INITIAL SET-UP COSTS.

I DONT HAVE TO VISIT ANY 'DODGY' DEALERS, WHO MAY HAVE ACCIDENTALLY LACED THE HERB BY A BAG OF [name drug here] SPILLING OVER THE BAG OF HERB.

I KNOW WHERE IT COMES FROM, THUS CONTROLLING WHAT GOES INTO IT (more specifially, what doesnt go into it!)

I WONT BE TEMPTED TO TRY ANY OTHER DRUGS IF I HAVE NO CONTACT WITH THE PEOPLE WHO DEAL THEM (Not that I would anyway, apart from shrooms).

I CAN CONTROL THE AMOUNT I CONSUME/SMOKE, SO I WONT BE STONED EVERY DAY. IF YOU HAVE ANY WORRIES ABOUT THIS, YOU CAN TAKE IT FROM ME, THUS BEING ABLE TO LIMIT MYSELF.

I WONT TELL ANYONE ABOUT IT, REDUCING THE RISK OF BEING CAUGHT BY THE POLICE.

THE POLICE ARE RATHER LAX WITH CANNABIS, AND IN THE U.K GROWING 6 PLANTS OR LESS IS CONSIDERED 'PERSONAL USE', AND YOU ONLY GET A FINE AT MOST. I WILL PAY THE FINE.