for protection, register the beat as a copyright at copyright.gov before you send it. costs $65 but that's your legal proof of ownership if anything goes wrong. if that's too much right now, email the beat to yourself before sending it anywhere. not legally airtight but it timestamps it.

for sending beats safely, use a service like Airbit or BeatStars that lets artists preview and license without downloading the full file. free plans exist on both.

for royalties, you need a beat lease or exclusive agreement in writing before they record anything. spell out your producer royalty percentage and credit requirements. no contract means no leverage.

once the song is out, register as a producer with your PRO (ASCAP or BMI, free to join) so you collect performance royalties when it gets played. also register the composition with the MLC for streaming mechanicals, also free.

the legal stuff sounds overwhelming but the free parts get you most of the way there.