Do they have textbooks on business? If so, where can I find them?

Here are a couple of web sites you might want to check out:

free business books on accounting, economics, mathematics, statistics, Exce.

Browse Economics, Finance, & Business Textbooks - The MIT Press

Hope this helps.

I would check out a used book store for old textbooks. Most of the time you can get an edition that is only a few years old for less than $10. University book stores will also sell used books but they will be more expensive.