Originally Posted by
Koan
Permanent Residency is something one applies for after some years in US of living or working on visa/ permission to stay
This is one 100% untrue. There is no requirement to be living or working in the U.S. prior to applying for permanent residency, either for family based or employment based petitions.
It is, however, common for employers to first sponsor a foreign worker for a non-immigrant work visa because it generally takes longer to get permanent residency processed and approved.