You may be underestimating the amount of work involved in being a landlord. If you find financially stable, reliable, non-destructive people, it's a nice income stream. Even so, they will expect you to fix problems sooner than you might get around to doing it for yourself. You probably shouldn't count on having your rooms rented for every month, you might lose a tenant and not have one ready to replace them immediately.

All this is general knowledge. There's probably information somewhere about the expected costs to being a landlord.

It still might make sense to buy the house.