However, he paid it off in less than 10 years so the last 10 years have been "rent" free.
Maybe rent free, but certainly not cost free.
There are three categories of PPoR tenure, and ALL cost money.
1. Owner - mortgage free
Has to pay for { council rates, water rates, insurances, maintenance, strata fees if applicable }
2. Owner - mortgage owing
Has to pay for { bank interest, council rates, water rates, insurances, maintenance, strata fees if applicable }
3. Tenant
Has to pay for { rent }
------------
Try not paying those bills (i.e. live for free) and you'll very quickly learn who is boss. People in category 1. (like your friend) do get kicked out if they don't pay their bills.
For category 1. it's the local authorities, for category 2. it's the bank and local authorities and for category 3. it's obviously the Landlord.
It's simply perpetuating those old myths like if you own your home it's cost free and rent money is dead money. Both are false.