Yeah, the idea of rent being required to pay for the property is stupid in general, and should not be allowed, but it seems various financial institutions do calculate that in among the variables for lending.

In the past, I did have a small 2bdrm not too far from a university. After I broke up with my partner at the time, I rented out the room but the non-bedroom areas of the house were common, so it felt more like a roommate situation (we also hung out together, had meals, etc)

Part of the money I got - which wasn't huge - went into saving, and part of that saving was the "oh shit fund". A few times, the "oh shit" moment was stuff that broke. down around the place, special levies by the strata, etc.

Anyone who is renting out a full place and not setting aside maintenance/repair money is an idiot or an asshole. Probably both.