Any person can post his or her own cash bond with the court or jail. If the defendant can’t afford to bond him or herself out of jail, any other person over the age of 18 can post the cash bond. If a defendant chooses to pursue a surety bail bond instead of a cash bond, most surety bail companies, like A-Affordable Bail Bonds, require a cosigner who is at least 18 years of age to sign the bail documents. Because of the differences in bond amounts and the uniqueness of circumstances, the criteria to qualify as a cosigner for a bond can vary bond to bond and bail company to bail company.