Having a solid contract helps a lot with providing proof of work and even broadening a client base. Non-compete clauses may be a main part of a contract that will benefit both parties if they can agree on rules for how a freelancer can add clients while working for an existing one. Without a contract, lots of freelancers will naturally want to pursue work opportunities where the original client may feel like that person is stepping on their toes. Getting all of these items out in the open will help to avoid a wide range of issues later on, and that’s part of the value of a solid written contract.
http://www.wahm.com/articles/freelance-software-projects-the-importance-of-contracts.html
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