No. With a well managed campaign, you will not spend anything more than your specified budget. And how much your budget should be is entirely up to you.
However, a lot of people have experienced overspending on their campaigns, unfortunately. This can happen if someone sets up a campaign for themselves without properly understanding how pay per click works or what all the settings mean.
When working with us, in the extremely unlikely event that your campaign does overspend over the course of a calendar month, our contract with you guarantees that we will refund the overspend.