The local sawmill gives me tons of wood. I've gotten everything from softwood to hardwood that's untreated. I also approached furniture makers, but most of their wood is treated. I got lucky and found a maker of heirloom- style furniture from heat- treated wood only.
Despite the size of your town/city, there's always someone trying to get rid of wood and branches or knows who to talk to!
Keep in mind that most any medium to large birds can destroy softwood the first day. Hardwood poses a problem.
Check out the sales at Drs. Foster and Smith. Also, this time of year is great for sales! Before you make things, check out the web unless you're a total DIYer.