There are 2 Water Shut Off Valve in each Unit, Both the Valves are unit owners responsibility to maintain and ensure it is in good working condition

First Valve in the Driveway which is called as Curb Stop / Water-Shut Off Valve. You need a plumber and a special key to open / close this valve. This can stop water supply for the unit

Second Valve should be in the basement water supply, most likely a Blue valve. This will also stop the water supply to the Unit. This is the primary water shut-off valve use to stop water supply.

Note: In case of emergency to avoid flooding you must ensure both the valves are in good working condition