I really like this person's DA
. They share their patterns and stuff and they look nice, I actually plan on using some for some cosplays down the line. But like most places you really shouldn't sell what you make unless it's your design.
As far as materials it depends on what kind of plush you plan on making. If it's human characters most people stiff use a fleece for the actual character and then they use left over fabric for clothes and such. If you own plushies you might be able to just look/feel them and sort of get an idea of what you can use.
Be aware that certain parts of pretty much all plushies can't be done on a machine so familiarize yourself with hand sewing if you aren't already.
Price depends on how you go about gathering your materials. You'll obviously know what your base material will cost (the fleece) but the other components depends on if you're getting everything new or using pre-existing stuff you have left over.