Depends on if he would be considered an employee or independent contractor. Anyone can hire someone on an hourly basis, that does not necessarily mean he is an employee.
The more this resembles a "gig", something you did outside the bounds of what your business normally does (worker brings own supplies, tools, and skills), the more that points to an independent contractor and means the artist owns the rights to the work, but there is prob an implied license to use the work on your part even if he does own the work. The more it looks like he was hired and was an employee (filled out a w2, had insurance, long term employee, did work that clearly falls within the scope of what your business deals with, you supplied the tools), the more it points to a "work made for hire" which would mean the company or employer owns the copyright.
http://www.copyright.gov/circs/circ09.pdf