Solar in Phoenix goes on a roof that has already been punished by the same sun the modules want. That is the whole caution. Tile over aged underlayment, foam that is due for a coating, and flat roofs with ponding are common, and covering them first is how a later leak becomes a miserable argument. West and south slopes take the hardest life. Shade is less than in a tree city, but a neighbor second story, a parapet, or a big citrus on the south can still matter. Start with a person on the roof, not a picture from above.
Ask what the attachment is for the roof you actually have. Tile needs a detail that does not crack the field and does not leave a hole in dried underlayment. Foam and flat roofs need a different fastening story. Ask who is responsible if a penetration leaks. Ask what happens to the array when the roof itself has to be replaced later. Ask whether the deck was inspected or merely assumed. A cooler curb, a skylight, and a vent already occupy space. Say what is up there.
The electrical panel is the second gate. Valley houses often already run a large condenser, and many run a pool. The panel may be full, hot, and old. Ask for that to be opened and described. Ask for the module and the inverter to be named, and ask whether electronics sit at each module or in one string unit. Ask who sees the monitoring and who you call when a portion goes quiet. Dust will film the glass between rains that barely happen. Ask how cleaning and access are expected to work without walking tile to death.
Ask who pulls the permit and who files the interconnection, and whether the system waits for permission before it operates. Ask whether you will own the equipment. Do not spend the call on a bill story. Spend it on the roof surface, the age, and the panel. Call the number on this page.