You can leave same day as your landing if you wanted to, the most important thing is to have a Canadian address for your PR card to be sent to , if not you will need to apply for a PRTD when back in your home country to be able to fly back.
If you have time also advisable on a short landing to attend Service Canada to get a SIN.
When you become a PR you commit to residing in Canada for 2 years out of every 5 years. So in the 5 years from initial landing you must accumulate a minimum 730 days. In theory this means following a short landing you could stay away for near 3 years but if you did that then must stay for 2 years without leaving at all.
After the initial 5 years the residency obligation is assessed on each new entry to the country, so 730 days in the 5 years preceding each entry. Failing to meet the 2 out of 5 years residency obligation can lead to PR status being revoked if discovered with any interaction with immigration for example such as entering the country, applying to renew a PR card or applying for a PRTD.
The previous poster referring to 3 out of 5 applies for citizenship applications where you would need to be physically resident in Canada for 3 years in the 5 years preceding a citizenship application.
