Here's the scenario. You're chatting with a buddy. You've got something he wants. You are willing to sell it. Back and forth you go until you agree on a great price. Everyone is happy.

That is everyone is happy until he reaches into his wallet and doesn't have the cash. That's OK. He'll get you tomorrow, right? But, what if his good sense catches up to him, and he changes his mind before tomorrow gets here? There goes the sale.

All of this can be avoided with a new app for your Android or iPhone. Square lets you use your phone as a credit card machine. And it's cheap, too. The app is free. They even send you a free card reader so you can swipe credit cards. Best of all - no minimums and no monthly fee. Service fees are straight forward. Use the card reader and it will cost you 2.75%. Type in the credit card number and it will set you back 3.5% plus $0.15.

Here are the details:

• App cost - FREE!
• Card reader - FREE!
• No monthly minimum.
• No monthly fees.
• Cost per transaction - 2.75% using card reader. 3.5% plus $0.15 without the reader.
• Cards accepted - Visa, MasterCard, American Express & Discover.
• Cash is deposited into your linked bank account within a few days.
• Super easy to use.

What makes it really cool? The purchaser signs with his or her finger. That's just neat.

Check it all out at SquareUP.com.