Well you might be able to fake an upkeep cost. If you give a negative bonus to income of some sort it would essentially be a building upkeep cost. Whether you reduce your income by $100 or increase your expenses by $100 its the same effect. The only thing is it's a percentage decrease to income so the more your city was making the more it would cost to upkeep the building. Come to think of it that's sort of like inflation.