If the government wants the defendant detained, the prosecutor will move for detention at the initial appearance. Bail in federal court is controlled by the Bail Reform Act, 18 USC § 3141 et seq.
There are some cases where the government gets an automatic three (court) days to prepare for a bail hearing. These are called "presumption" cases, for offenses such as drug dealing, child sex offenses including child pornography, and bank robbery. See 18 USC § 3142 (f)(1), (2). The government may also try to prove that the defendant is a flight risk, or a danger to the community - in those cases, the government also gets three days to prepare for the bail hearing.
The defense can also ask for up to five days to prepare for the bail hearing. Defendants seeking bail are then referred to a United States Probation Officer for a pretrial services interview. The Probation Officer who interviews the defendant prepares a short life background and criminal history for the court. The public defender or CJA panel counsel may accompany the defendant to the pretrial services interview.
A magistrate must decide whether or not there are any conditions of bond to reasonably assure the defendant is not a flight risk and is not a danger to the community. Most bonds in federal court do not require the posting of money or property. They are called "unsecured" bonds. If the defendant is released at the bail hearing, it is often with conditions. Typical conditions include reporting to United States Probation, drug testing, and district-wide travel restrictions.