First of all, he does not need a valid visitor visa if he is not intending on leaving Canada during the application process. The visa is a travel document and is not required if he is not travelling outside of Canada.
If he wants to study or work, he can apply for a study or work permit during the application process.
If he doesn’t need to work and doesn’t want to study, there is nothing he needs to do until you receive a decision on the application.
If the decision is positive, he will become a permanent resident.
If the decision is negative, he will have to leave Canada.