So wonder upgrades have both a maintenance cost (the X/a month) as well as a fixed cost?
What happens if you can no longer afford the maintenance? Can you scrap upgrades?
The cost is only while building them.
And yes, they will have both a flat cost that you pay straight up, and a ticking cost that will deduct money each month while the construction is ongoing.
If you can't afford the ticking cost, the construction will be put on hold until you're back in the green again.
Upgrades can be scrapped while they are in construction, but: NO REFUNDS!