How to jailbreak my iphone 4 version 7.0?

I'm looking for an untethered jailbreak that is free for mac computer

All jailbreaks are free. That's the first point. If it's not free, it's most likely not real.

As for iOS 7, there isn't a jailbreak out just yet… But it's coming.

The best place to check for real jailbreaks is http://www.isthereajailbreak.com/

You will only find FREE, genuine jailbreaks there from all the jailbreakers around the world.

Http://www.youtube.com/user/iOS7JB