Does the CIA hire assassins?

Yes. They are called mercenaries.

They usually go in wars and kill people for money.

The government also hire assassins to kill ennemies that they can not get using legal means through various countries.

Normal people hire assassins from Mafia and Gang members, like Besa Mafia, google it. Some are willing to do murder for as lowe as $5000 ( shot and run ) while sniper hitmen can charge over $30 000 for a hit