Does a valid Contract have to be in writing?

The simple answer is: no. A contract is an agreement. It is legally defined as a "meeting of the minds". If you can prove that there is a meeting of the minds, you have proof of a contract. A meeting of the minds is when two parties agree to the same basic elements. Those elements are: Making an offer and accepting that same offer. The offer must be specific enough so as to discern what exactly is being offered, when, and for what value in exchange (point number 2 below) ; An exchange of value that is agreed upon (e.g. services, money, goods...