I strongly suggest postponing the grow until you have your own place. There are several reasons and they are as follows...
- If you get busted by the law for some odd reason, your parents will be held responsible. If you care about them at all, you won't put them at risk.
- Theres really no way to grow pot in their house without them finding out. At some point, they will go into the attic for some reason or another... or they will smell it... and then you will be in a world of shit.
- Its just not worth the risks and the worrying you'll have to endure.
- Using your cousin's shed also comes with unwanted risks. Assuming that your cousin will know about it, you'll run the huge risk of your cousin going in there and taking buds behind your back. You really can't trust people when weed is involved. One day, he'll be jonesin' to get stoned and he'll decide to go out to the shed and snag a top bud. You'll come to check on your ladies and you'll see what happened. You'll be upset and then you and your cousin will have issues.
- Its best to have a grow that NOBODY knows about. Having your own place makes this much easier.