I'm pretty sure he means 20 wet grams, which would equal about 2 grams dried. And as far as legality in the US, I have bought a kit from a head shop before that has instructions in it. It is actually pretty easy to set up your own grow kit as long as you have a pressure cooker to sterilize everything, or you can buy pre-sterilized mushroom compost and a mycobag. Colonize the bag and then case it in the compost inside a rubbermaid container. It's pretty cheap, and for the price of a kit, one could get substantially greater yield. The most expensive thing is the spore print or syringe, and once you've grown some you can make your own prints, and reuse everything but the compost, so subsequent grows are even cheaper. Check out shroomery.com, there's tons of info on it.