Contract for Computer Game development business

I need a contract to outline all the important concerns for starting a business. The business set up is: - I pay 1 other person a weekly wage, who is based in the USA. I am in the UK. - He owns 10% of any software he creates for me. - the other 90% is owned by myself - He creates all the work and is supplying artwork from friends and contacts, and will be taking full liability for the use of them. This doesn't need to be the most complicated contract in the world, we have a good working arrangement and i don't want to scare him off with a long contract that seeks only to protect myself. All it needs to do is specificy all the necessary legal bits in case there is any dispute down the line etc.