Thossil over the life of the mortgage your rent increases and if it doesn't cover your whole costs in the early stages it will within 5 to 10 years easily.
Right now I can purchase a property for $150k in a capital city @ interest rate of 7% my payments would be approx $12k, now that same property I can rent out for around $240 a week easily which is about $12.5k. Now rates and other costs are around $2k. Even if it takes 10 years to cover all your costs that is only another $20k you would have had to kick in and it would be more than returned to you in years 11 to 30 of a 30 year loan.
Now I can do far better than that right now a) I can buy property cheaper and with a little bit of effort and money really smarten it up and get more than $240 a week - end result property basically costs me nothing from day one. I may be negative from a taxation point of view because of depreciation but that is just further cash in my pocket. At the end of the day I will own an asset worth $150k today OUTRIGHT in 30 years that has cost me nothing. That is wealth building the long term sustainable way.