1) Business associate 2) Equal business associate 3) Partner 
• (n.) One who is jointly concerned with one or more persons in business, etc.; a partner; an associate; a partaker; a sharer.
One who is partner with one or more then one person in a business undertaking.
Co·part'ner noun One who is jointly concerned with one or more persons in business, etc.; a partner; an associate; a partaker; a sharer. « the associates and copartners of our loss. Milton. » 
[n] - a joint partner (as in a business enterprise)
noun a joint partner (as in a business enterprise)
a partner or associate, as in a business.