This weekend is the Giant Book Sale at the Union Street branch of the Mid-Columbia Library at 1620 S. Union, Kennewick. Books for 25 cents to a dollar are available Friday 9 a.m. to 6 p.m., Saturday 9 to 5 p.m. and Sunday 1 to 4 p.m. Library book sales are a great way to teach kids about entrepreneurship.

Here's how it works:

Libraries hold sales as fundraisers and to get rid of old books that are rarely checked out. Many of these books can be sold on Ebay or Amazon for a profit.

To get started, create an account on these sites. For Amazon, the option is in the top right of the page. After you're registered, check the menu for "Your Seller Account" and set one up. Your rating as a seller is dependent on you offering books in good condition, being honest in your description, fair in your price, and shipping the books quickly. If you try to trick or swindle people your user rating will get trashed and no one will buy from you.

You must be careful, however, because other people are on to this library book sale tactic and can push down prices for some books.

In fact, there are HUNDREDS of popular titles that are sold online for ONLY A PENNY! That's right, a penny. I've done a little research and learned that some book retailers use Amazon to get rid of stock. Making sales for a penny is a form of advertising. Some will keep your email or account information and send you ads for upcoming book sales on their website.

Here's listings for Harry Potter and the Sorcerer's Stone in paperback:

I have a personal theory that the shipping cost Amazon adds to orders and passes on to sellers is generous. I've only sold about half a dozen books online but I actually profited from the shipping on all but one!

Yes, I profited from the shipping. If someone sold a paperback copy of Jurassic Park on for a penny, and Amazon passed on $2 extra for shipping, and USPS only charged $1.50, then you've made $0.51 profit. Do that enough times, it's enough money to make it worth your trouble.

Back to the original plan: buy low sell high.

How do you know what books sell for a penny and what ones are going for $50? A SMARTPHONE! I've come back from library sales only to discover half my load is worth a penny while books I saw, but passed up, are going for $20, $25, even $50.

There are some people who take this VERY seriously and have a bar code scanner attachment for their smartphone. They wait outside thrift stores and rush to scan new arrivals for potential profit makers.

This is not a get-rich-quick scheme. You must have room to store dozens of books that will take time to sell. I've been in the embarrassing situation of loaning a book to a friend only to demand it back two months later because it sold. My sister had to do that to me once, as well. Some sell quickly, others go for a good price after many weeks (perhaps once the penny books get bought up?)

So if you're out of work and have a mortgage to meet, this isn't your strategy. But if your kids are bored of lemonade stands and mowing lawns, this is definitely a sound plan -- just be prepared for minimal profit margins. Quantity and skill are essential to make it worth your time.

Flickr, San Jose Library
Flickr, San Jose Library

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