Of course, like everything, there is a range. Some will work on an Hourly , daily or all-in basis. Their rate depends on their skill level and experience. Many "all-in" producers in L.A. charge about $50 an hour or $300 for a 10-hour day. If you're a more established artist and have a track record or a heavy sales/streams or high -paying synch placements you can negotiate a percentage of revenue. Like $300 up front, all in for a single, plus 20% of all revenue over $10,000. The $10,000 bench mark is so you don't have to pay out $2 checks every four months if the song doesn't make much money. But if it makes $10,000 you pay your producer from dollar one. So if he's making 20%, he gets $2,000 for $10,000 gross song revenue. Often times the song won't sell much but gets placed in a commercial for $200,000. (Yes, this happen to indie artists all the time.)
Ari Herstand -How to Make It in the New Music Business.