If I buy a holiday home (without tax breaks) and rent out (very) occasionally.
Can I offset the mortgage income against rental income on other properties?
As far as I know you can only offset mortgage interest on loans used to buy/renovate an investment property against rental income from that property and not from others. I could be wrong though...
You can offset the mortgage interest payments on all rental properties against profiits from other properties that are rented. But I don't think you could just rent it for one week and then offset the mortgage if that is the point of your question.