A property qualifies as your principal residence for any year if it meets all of the following four conditions:

It is a housing unit, a leasehold interest in a housing unit, or a share of the capital stock of a co-operative housing corporation you acquire only to get the right to inhabit a housing unit owned by that corporation.
You own the property alone or jointly with another person.
You, your current or former spouse or common-law partner, or any of your children lived in it at some time during the year.
You designate the property as your principal residence.