You might want to look into Quickbooks by Intuit. Quickbooks can do what you need, and so much more. So it's a wise investment even if you don't need all of its functionality (and there's plenty) right now--you'll grow into it. That means you won't be making decisions about business management software every time your business grows to the next level.
Additionally, if by chance you need functionality that Quickbooks doesn't have, there are many programmers who do customization for Quickbooks, so either way you'll win.
Quickbooks also often offers a trial version of its software, so you can try it out without spending a dime.