There is a saying, a verbal contract isn't worth the paper its written on. The exception being marriage; one of the few remaining verbal contracts that are actionable. Other than marriage you should get everything in writing.
nothing at all.... trust me on this one, if i had a quarter everytime a verbal contract was broken id be richer than bill gates :O
Definitely better than none..written MUCH better..if verbal, a good witness would be wise....
As binding as you want to be known for a person who keeps their promises/word.