The odds of you buying a new ps3 on a jailbreakable (hackable) firmware (3.55 or lower) is close to none. A second hand console however you may have better luck.
Now, if the ps3 is however on a higher firmware than 3.55, you can buy and install a E3 Flasher to downgrade the ps3 and jailbreak it (this requires opening up the ps3 console (and soldering if using the old fat ps3)).

The idea of a jailbroken ps3 is to run homebrew applications such as emulators, but the core reason people do is for backup managers to make copies of games to the hard drive to "legitimately back-up their purchased games", so they say.

Hope I helped.