No reason for heated discussions. We are well aware of the pros and cons of a third child. We will sort that out among ourselves and, if necessary, bite the bullet and simply continue renting.
By the way, I see the biggest hurdle regarding the house only indirectly in the costs. Rather, we have to severely limit our selection of houses because ideally we need 5+ rooms (including a study). That of course then has a direct impact on the purchase price. Surely compromises can still be made there, but most houses on the market do not appeal to us in terms of size and layout. Regarding childcare and a second income, we are well positioned in the long term with both grandparents nearby.