Sounds like you have an electric car, if so you are likely already set. Most any car ESC has a built in BEC. Generally in the 5 to 6 volt range. The 3-wire plug to the receiver powers the receiver and then the servo.

Yes, a BEC (battery eliminator circuit) is just a RC term for a voltage regulator. Mostly for nitro with lipo receiver pack, and 1/8 electrics.