Here's another fast and easy way to make money. People are always getting rid of used books. When people buy books, they read them once (maybe twice) then put them up on a shelf and forget about them until they need the room. Then they go in boxes in the basement. When they finally need room in the basement and look for something to get rid of, boxes of old books are usually the first to go. People don't even try to make a buck. Often, they even hire someone to cart the boxes of books off to the local dump.
What you can do is start by advertising your services to remove unwanted books. You can charge a low fee, say $10 per box. Believe it or not, people will pay that! But the real secret is that these books that they are paying you to get rid of are worth money! That is because smart people do not buy books from retail shops. They look for cheap ways to buy. That's where you come in. Advertise that once a month you will sponsor a giant book sale. Dust off those books and set up display tables in some shopping center parking lot. All you need is thirty locations, and you can do a book sale every day. Since the books cost you nothing (remember -- you were paid to take them) anything you charge is profit. Sell them for $3 per book. Sell one hundred and that's $300 profit in you pocket with no expenses on your part. Thirty times a month means you can earn $9,000/month or over $100,000 a year!
Don't worry about running out of books. The same people who buy books from you will pay you to take them back after a few months of gathering dust! So what are you waiting for. Go get rich!