(1) If you * acquire an * ownership interest in a * dwelling that is to become your main residence and you still have your ownership interest in your existing main residence, both dwellings are treated as your main residence for the shorter of:
(a) 6 months ending when your ownership interest in your existing main residence ends; or
(b) the period between the acquisition of the new ownership interest and the time when the ownership interest referred to in paragraph (a) ends.
(2) Subsection (1) only applies if:
(a) your existing main residence was your main residence for a continuous period of at least 3 months in the 12 months ending when your ownership interest in it ends; and
(b) your existing main residence was not used for the * purpose of producing assessable income in any part of that 12 month period when it was not your main residence.