It only appears like a vicious circle. In practice, student visas (or marriages) bring the person in, then the person finds work, real work, then tries to persuade the administration that she doesn't "take the place" of a local who lives on social help, ie, there was no one else available for the job then and there. Once this is done (accompanying paperwork included), employee visa is at hand.

Free at last! Free at last! Thank God Almighty, we are free at last! (Martin Luther King)