A contract is mandatory for any commission. Write down every detail in the contract, such as the size and media of the artwork, your compensation, due dates for payments, who is responsible for framing, installation, delivery of the artwork, etc. If your client balks at signing a contract, WALK AWAY.
Contracts like an artist agreement help avoid miscommunications and confusion over the rights and responsibilities of both parties involved. Artist agreements typically include availability expectations, performance markers, and licensing or ownership rights of the works created during the partnership.
The artist agreement is between two parties who agree to work on specific projects and it governs their relations inter se. It is necessary to have a written agreement with definitive terms to avoid any disputes in the future between the parties.
It is illegal. Once any piece of work is created, it is automatically copyrighted. This includes art, photography, music, etc. You have to have the creator's written permission before you use it anyway at all. If you want more information, you can search for copyright infringement.
An artist statement is a not-too-long series of sentences that describe what you make and why you make it. It's a stand-in for you, the artist, talking to someone about your work in a way that adds to their experience of viewing that work.
The agreement or contract is the legal document between an artist or owner of an artwork and a borrowing institution, or between an exhibition organiser and the host venue. They are written to specify details about work to be undertaken and the expected outcomes.