I have an owner occupier mortgage on my primary residence. My brother would like to loan me some money to use as an extra payment on my mortgage, to reduce my mortgage interest payments. I would pay my brother back at some (unknown) point in the future.
If at some point I convert my primary residence to an investment property & withdraw money from the mortgage to pay back my brother, will interest payments on the full outstanding mortgage be tax deductible? Or would the part that I withdrew to pay back my brother not be? Does the timing of withdrawing from the mortgage - before or after converting to an investment property - make a difference?