If you are the unmarried child or spouse of a permanent resident, you too can apply for a green card. A child is anyone under 21 years of age who is not married. Because of this, turning 21 before or during the green card process can delay your visa.
There are other ways to qualify for a green card without having a permanent job offer. You can qualify for a green card for work as an investor, entrepreneur, self-petition, or eligible job sector or title.