Very common, and in some countries practically unavoidable. Where bureaucracy is heavily paper-based, conducted only in the local language, or dependent on knowing unwritten conventions, a good local agent or lawyer saves weeks and prevents expensive missteps. Sworn or certified translators are a separate necessity in many systems, since offices often accept only translations bearing an official stamp.
Cost structures vary: translators typically charge per page or document, agents per procedure, and lawyers per hour or as a flat fee for defined work like a residence application. Rather than quoting figures that go stale quickly, ask two or three providers for written quotes and compare; large gaps reveal the fair range fast.
Do the basic diligence you would at home. Check licensing where the profession is regulated, especially for immigration advice, which many countries restrict to authorized practitioners. Get the scope in writing, never surrender original documents without a receipt, and walk away from anyone claiming special relationships with officials or guaranteed outcomes.