There are many ways to download karaoke songs for free, including from sites like Youtube, or specialty sites that offer a library of music. While most sites offer a free trial period, a subscription is sometimes required after that period ends to continue using the service.
Downloading karaoke songs from Youtube does not require a subscription, but is a legal gray area. Since the videos listed on Youtube may contain copyrighted material, it may not be legal to actually download them to a personal computer or other device. Downloading karaoke songs in this way also requires extra software or a third-party service.