Not sure I understand your first question. Canada has several different immigration programs. You'll need to research each to determine what the requirements are for PR.
To work in Canada before they become PRs, your parents will first need to obtain a full time job offer from a Canadian employer. Next, that employer will need to obtain an approved LMIA. This involves first advertising the job for at least a month to prove no Canadian could be found for the role. Then, the employer needs to apply for the LMIA and pay a $1K fee. Processing can take several months with no guarantee of approval. Generally speaking, it tends to be extremely difficult to find employers willing to go through the LMIA process.