Sadly at the moment you can only get back half of the units you spent on those extra condos.
Press Esc and then find the section in the pause menu called “Inventory”, click that button to open up the pause menu inventory that shows every single item that you own.
Then locate the “Condo: Smooth Autumn” and “Condo: Smooth Dirt” item, either manually or by using the search feature in the inventory.
Once you’ve found them, right click on said condo items and press the “sell” button that pops up.
This will give you back the 50% of the units spent on the item.
There will be a way to get a full refund in the future:
As mentioned by Caboose in an earlier thread, at one point or another they will have made the tower express able to automatically refund all the cash you might have accidentally spent on extra condos.
It’s unlikely that the function has been added yet since that was said just 6 days ago, although you can always wait with the whole selling extra condos for a refund until said function has been added.
The tower express in question can be found here:
https://express.towerunite.com/