Prescott Nat'l Bank v. Head
In Prescott Nat'l Bank v. Head, 11 Ariz. 213, 90 P. 328, 330 (Ariz. 1907), the plaintiff acted as a surety on a bond for the lender in a construction project, but also sold material to the contractor. Id. at 329.
The court held that there was nothing inherently inequitable about such an arrangement, noting that at worst the dual obligations could be set off against one another, such that both could be honored. Id. at 330.