After delivery, which monthly expenses would you add to the budget?

In addition to common expenses and taxes, I would reserve money for small repairs and furnishing. Even a new apartment starts generating costs once it is used.

If the plan is to rent the unit, I would add brokerage fees, vacancy periods and management. Gross rent is never the same as net rent.

I would ask when common expenses start and who manages the building. That date may not exactly match the date when the owner begins using the unit.