You could also look at it the other way and say you have sunk costs either way, either on rent or on running costs for your (owned) property: mortgage interest,

You could also look at it the other way and say you have sunk costs either way, either on rent or on running costs for your (owned) property: mortgage interest, property taxes, maintenance, opportunity cost for your down payment. The question is how do you invest the extra leftover money: in home equity tied to the property with running costs, or in other investments (stocks, bonds, your own business)?