Can a minor (17 years) sign a business agreement without a parent? Also, can a non-lawyer create an agreement between parties?

Typically a minor can not sign a business agreement without a parent but there are many things a minor can do without a parent, so an attorney would need to see what "business agreement" you are referring to. Non-lawyers create agreements all the time. Legalzoom is a site dedicated to having non-lawyers prepare all sorts of legal documents. Para-legals draft legal documents all the time as do many small business owners, but it is always best to have an attorney review their work if you can afford one.