LLC is going to depend on the state, but most are really simple if you are actually a sole proprietor.
You file a basic articles of organization with your secretary of state. This will cost $100 or so and can probably be done via a website.
Generally, in this case, you'd be taxed once. . . e.g. all gains or losses are passed from the LLC to your personal tax return.
You could set up for double taxation if you wanted (tax for the biz, then tax on your...