The Court sets the bond amount. You can put up that much in cash or you can pay a fee to your bail bondsman to insure your appearance in court on a later date. The fee is usually a percentage of the bond, since greater risks cost more than lower risks.
When a bondsman posts bail for you, you will have signed contract for payment. You will also be subject to the bondsman arresting you and delivering you to court or to jail.
Normally the cash needed for a bond is 10 percent of the bond amount. So, in your example that would be 50,000.00 dollars.