It's incredibly rare that a beardie will bite. They are generally calm and docile animals - in fact darn right lazy sometimes!

As Cassie said, life span is around 10-12 years.

Well...it's a toughie. There are some really good pet shops out there - but then we also have the ones who are only in it for the money. The kind who keep babies on either sand or even worse, beech chippings.
I pulled up a pet shop about this once, and he simply said it because the viv looks nicer. I sure as hell would rather have a healthy lizard - then one running a high risk of impaction.
Expect to pay around £100 in a pet shop. I can put you in touch with breeders - some sell for just £30.

Where abouts are you?

I got mine at 7 weeks old, and as already mentioned juvenile mortality is high, but with the proper care, you will be fine.

Another mistake people make is feeding too large of feeder. The general rule is to judge by the gap in between their eyes, feeder insects should always be smaller than this. Feeding live food that's too big can cause all sorts of problems - mainly in babies.

Once you get one, you won't look back, they are so adorable and surprisingly affectionate.