I did nothing except supply the lot and money.

Not sure how far you are from Chicago proper, but the ULI (Urban Land Institute) is a global group with chapters in most big cities. 

As of early 2024, inventory levels were about 3.79% higher than the five-year quarterly average, indicating a slow but steady increase in supply​​.Demand and Buyer BehaviorThe Birmingham market will continue to attract out-of-state buyers, with significant interest from cities like Chicago.

It’s a 3 bd 3 ba condo and I supply all of the utilities and WiFi.

The market is on the move with a median sold price of $576,500 and a 5.41 Months Supply of inventory.

Sure the shingles run a bit over $100 a sq , but you need felt paper , drip edge , flashing , coil nails , misc supplies , delivery , disposal costs , labor , insurance , sales commissions , overhead , whats left is profit , and it it runs around 20% . 

And yes, there is a limited supply.

I don't know what the deposit is but even if you figure just supplies for some of this stuff it will add up. 

Is there more supply in the area?

GP’s should supply stress tests.