If you do this as a one-off - you'll pay Capital Gains. If it becomes a pattern, the revenue may seek to tax you as a trader (in partnership with your Dad).
If this place is somewhere you actually live, you may get away with no Capital Gains on your share of any profit, but if its a hovel, you won't
I'm afraid its along time since i practiced as an accountant in the Tax field. Get a decent accountant