Start with Bandlab or Cymatics. Download one pack. Do not go on a hoarding spree (you will never use 4,000 vocal samples). Pick 20 that fit your vibe—deep voices for techno, energetic shouts for house, whisper-soft hooks for lo-fi.
Services like Splice or Arcade offer vocal cues via subscription. While not strictly "free," they offer free trials. If you download a cue during a trial and use it in a track that blows up, you are usually fine. However, if you monetize a video using a "Free" pack from a random forum, you risk demonetization. Vocal Cue Pack Free Download
But sourcing high-quality, royalty-free vocal shouts, chants, and drops can be expensive. This is where the search for a becomes a mission for thousands of creators every single day. Start with Bandlab or Cymatics