South Point has become the fourth company to offer a mobile sports betting app after launching its service Tuesday at five Nevada locations, including four in Las Vegas. The app, available for the iPhone, iPad, Android and Android tablets, is free to download and resembles the William Hill app that has been available in Nevada for more than a year. South Point Casino began advertising its app Friday in its sports book. A website is available at nvsportsbooks.com to answer questions gamblers might have. The app requires a minimum $100 deposit. Out-of-state residents are allowed to sign up and fund…