The mortgage side is usually the easier fix. Most residential mortgages assume an owner-occupied property, and a lender may require the loan to be switched to a rental or investment product, which can carry a different rate and different qualifying rules, including CMHC's standard 39 percent and 44 percent income ratios if you are refinancing.
The tax side is the one people miss. The Canada Revenue Agency's principal residence exemption shelters gains on the home you live in, but once it becomes a rental, a change in use can be treated as if you sold and immediately reacquired the property, starting the clock on capital gains from that value forward rather than your original purchase price.
None of that means keeping it is a bad idea, only that the decision should be made with real numbers on both sides, not just the rent cheque. Get your hand-reviewed valuation from Joel Dyck.