Solar in Washington starts with the roof and the sky you actually have. West of the Cascades, long cloud and shade from tall firs matter as much as the hardware. East of the Cascades, stronger sun comes with wind, hail, and summer heat on the roof deck. In both places the first question is whether the covering and the deck can carry an array, or whether the covering should be renewed before anything is fastened to it. Moss, grit, and a soft bay are reasons to stop and talk about the roof.
Walk the shade honestly. A slope buried in cedar shade for half the day is not an open slope, even if the house faces the right direction. Say the roof material, whether moss owns the north side, and whether any plane already leaks. Ask how the feet will be flashed so the wet season, or the basin wind, does not turn each bracket into a drip. Skip sheathing on an older house may not hold a mount the way a later plywood deck will. Say what the attic wood looks like after rain.
Ask where the inverter and the shutoff would live. An attic that bakes in a basin summer, or a garage that stays damp all winter on the west side, is part of the equipment decision. Ask what the house does when utility power drops, and whether you even want the system to run in an outage or only while the grid is up. That is a design choice, not a slogan.
If an association or a permit office has a say, ask what must be settled before work starts. Storms, limbs, and hail do not become polite because hardware is on the slope. Ask how a later roof repair is supposed to happen with modules in the way. You are not drawing the rack on the phone. You are refusing to treat a tired roof as a shelf.
Have a ground look at the south slope and the trees, know whether you would own the equipment, and call with the town before a sky picture talks you into a bad deck. The roof can carry this or it cannot. Call the number on this page.