How safe is it to jailbreak my IPhone 4s?

How safe would it be to jailbreak my Iphone 4s, and would it have an impact on my phones performance? I've heard there's a chance that it will break my phone beyond repair and Apple won't do anything to fix it, is this true? Is getting rid of cydia or un-jailbreaking my phone still possible if I want to get rid of it?

I've had this phone for about 18 months now so maybe it's worth the risk?

Added (1). Also how much storage will cydia and jailbreaking my phone take up. And has anyone got the official web address for where I can jailbreak my phone?

Its not safe at all. And yes its true that if you jailbreak it they won't fix it for you. And you can't get rid of a jailbreak program once its in there. Some how it messes up everything on your hard drive.

Jailbreaking is NOT safe at all… LOL… Only you can decide on the risk. I personally laugh at people who beg for help to un-brick their iPhones.