Hi,
I did similar edits for over two years for one of my clients. The only difference was that those projects came from Digital Juice, some of them from VideoHive.
To answer your questions. First of all, long time partnership is what I am looking for. I can do 4-6 videos per day, so that would be 20-30 per week, which gives us 80-120 per month, which is crazy, I know but I can do that. As for the price per video. If you can provide me work for 10-15 videos per month, the price would be $40/video. If you can provide me 30 and more per month, price would be $30/video. In case you will have even more work, we can discuss it further.
As for the music. If we will use music from Audiojungle, then it's a additional charge. For example: 30bucks for video plus 15 bucks for the track. Of course, I can buy it if necessary.
If you will be interested, I can show some animations I did based on DJ projects. In the meantime, check the rest of my work at apaczos,com
Oh, and I didn't mention...first video would be free.
Looking forward to hear from you.
All the Best!
Pawel