Hey Melons
As the songwriter you are automatically entitled to 50% of your Publishing royalties from the base income. So he couldn´t take 50% of yours and then have his publishing company take another percentage on top of that. If he is an artist, his leverage should be on the mechanical royalties, which basically mean the sale of his songs either through digital download or on CD. I would be very cautious about signing this agreement until you get a music lawyer to check it over. You should also ask the artist some very specific questions about how s/he plans to promote and market the songs. It may seem like a good deal on paper, but don´t be afraid to ask some challenging questions. If someone really wants your song then they´ll be happy to answer them.
If you´re not already, sign up to the Musician´s Union, GISC, BASCA or a similar body who will give you free legal advice as a member. If the song is successful, the membership fee will be more than worth it.
Good luck with it.
