Good question,but he doesn't just want to buy an investment property,he has other whelin and dealin ideas.He can afford to retire now,but has a good job that still pays well. But me thinks it is for a couple of other reasons also.
1/The obvious--sentiment of owning his home outright.
2/Using the equity,all or some?,to buy an investment long term,probaly a rental property-- the rest we know
3/Play the market,he has had more winners than losers
But I think it is mindset about tax,and he reckons he has paid enough.Which I agree considering he paid $24K in tax last year and the year before and before,and yes he sal sacrificed