Most DJ software these days has tempo/key adjustment as well as hooks to connect to subscription karaoke services (basically Spotify for karaoke). Unless I had a business with a ton of old school gear, that's how I'd run a karaoke company nowadays. No worries about licensing/rights for songs, updating your collection with the autotuned robot song of the week, and easy to connect a laptop/mixer to an existing sound system or your own PA.