“One had to apply for permanent residency (green card) at an embassy or consulate within their home country. It took 18++ months and you had to have a sponsor guaranteeing you would not need government assistance”
The wait depends on the country and the individual. For a normal individual, the wait is in years, like 5 years, after the initial process. For countries such as China or India, the wait is in decades, for the green card.
Not sure about the guarantee of non gubmint assistance. Once you have green card, you are guaranteed all welfare rights of the citizen except to vote or hold office.
I was in LE in the 60’s and handled several cases in which permanent residents were involved. Turns out they had applied under false pretenses and lost their permanent status.