The easiest way to grow mushrooms at home is with a five gallon bucket full of coffee grounds, and some Oyster Mushroom spawn. Spent coffee grounds can almost always be obtained free from a nearby coffee shop. Oyster mushroom spawn can be purchased online from Amazon or from a mushroom lab near you. Detailed instructions for putting together a five gallon mushroom farm can be found http://www.stormthecastle.com/terrarium/how-to-grow-mushrooms.htm
Yellow Oyster Mushrooms They are one of the most profitable exotic mushrooms to grow; a huge demand for them. Last year:, 1.5+ million lbs of exotic mushrooms were grown. High demand; very easy to grow; take about 6 weeks from start to harvest time; no full-time commitment necessary. You can still have a full-time job & be a successful mushroom grower. You need just a few hours a week to spare. Sell: $10-$15 per Kg
This guy has tons of free PDF's and PowerPoints on growing and caring for mushrooms. He also has stuff on mushroom hunting (mushroom foraging), etc. He has workshops too, on growing and finding mushrooms.
"How to collect Oyster Mushroom spores, so you can grow your own at home, like I'm doing now! Instead of eating all of my mushrooms, I'll be harvesting spores for the next batch. ♥" -Homesteading share