i just need help making a beat to start a song

i just want to get started making music but i need guidance on how to really start. I just need a beat to rap over.

Additional info:
I'm interested in working with a very experienced mixer. . I don't have a hard deadline for this. The song has less than 10 tracks recorded that need mixing. I need the vocals tuned as well. I'll need you to master it too if possible.