If you agree to be responsible for an unsecured bond in federal court essentially what you are doing is signing a promise to pay. At the outset it doesn't cost any money. If your boyfriend fails to show up for court you are liable for the amount of the unsecured bond.
The amount of the bonds vary dramatically depending on a variety of factors. Pretrial services can tell you the amount of the bond they are recommending but you won't know the bond amount until the judge makes the actual order.
The answers to these questions are intended for informational purposes. The attorney-client privilege does not attach and will not attach unless a written contact is entered into with Ms. Daly's firm. CIRCULAR 230 DISCLOSURE: If the above relates to a tax matter then, pursuant to Treasury Department Rules, we must advise you of the following: The advice contained in this communication was not intended or written to be used and cannot be used for the purpose of avoiding penalties that may be imposed by the Internal Revenue Service. Under the applicable Rules, a taxpayer may rely on our advice to avoid penalties only if the advice is reflected in a more formal tax opinion that conforms to IRS standards
I would be very careful if I were you. I would wonder why his parents or siblings are not signing the bond. You could be putting your financial security at stake as well as your relationship.