Where to get non-copyrighted, good-sounding vocals for RVC input? Do I need that?

My (maybe wrong) understanding is that RVC requires input & target vocals, which means I need to supply vocals that sound excellent.

Where do people get non-copyrighted vocals to use for RVC? Do I just need to use something like TTS and supply that audio and maybe RVC can correct it into some well sounding vocals?

Know it's a noob-y question, so apologies! Thank you.