You are assuming that your rental payment > mortgage payment based on current market value of the property. That's absolutely not the case in the majority of situations (which is why people choose to rent vs. own: you can live in a property that you would never be able to afford to buy, if you choose to rent). Rents are often a good deal because the landlord does not want to sell, but have a source of passive income, have the house be occupied and close to cash-flow positive while it grows in value over decades (a nice nest-egg) etc.

You truly can not determine if you can afford to buy a place until you take a multitude of factors into account, and they vary for each person and each property.