Health: Does a bookkeeper need a business associate's agreement in a medical office?

Will he be an employee or independent contractor? I would consider entering a written agreement that explains the terms of the professional relationship. It should include a confidentiality agreement. In an abundance of caution, it would be helpful to include a provision related to medical privacy laws.

If he is not business associate (employee,if you mean by that), then he does not. My colleague is right. However you wan the working relationship be, you need an agreement corresponding to it.

I don't understand to what extent you meant by a business associate's agreement. If you meant an employee or independent contractor's agreement it all depends. Based on the descriptions of his position, I would advise a Non-Disclosure Agreement is essential. You should protect your trade secrets i.e. your healthcare practice's financial information ( and any other relevant info relating to your business) when this person leaves this position.