Is we talking turn off valve? Slab house, national code requires a turn off valve where the supply pipe clears the top of the slab. That is usually under a sink, bathroom or kitchen. That will be a valve kind of barely sticking out of the wall under the sink.
Some warm weather houses run the line up and into the side of the house. Have seen this in Houston, with busted frozen pipes. Blue Norther, don't you know!
All water systems everywhere require a turn off at the meter. Usually in the meter hole, you need a special tool or crescent wrench with a strong arm.
Pressure reducer? Why yes, I have had one. Too much water pressure can be hazardous to your health. When I had a copper line burst under my kitchen floor, my blood pressure went off the scale. When the water system manager said, why yes, you do do have high pressure. You need a pressure regulator. I thought everybody already knew that.
Sometimes my ESP just don't work!