NOT his problem; you supplied the crappy lumber.  

Wholesalers serve a purpose…They supply “rehabbers” with many times vacant run down houses that need a complete overhaul to bring back to market standards.

Supply houses do offer credit , net 10 days usually then there is a carry charge after that .

First, they dropped off my roof supplies (pallets of material) on 8/31.

There is no guarantee the next tenant will be any better, they may be dirtier and not pay rent at all.I have inherited heavy smokers, but they have already been smoking in the unit for years. 

Meaning demand (in certain markets) may outpace supply in the long run.4.

Regulation will put downward pressure on supply which will exacerbate the housing "crisis" in Portland Metro which will mean less competition and higher long term rents. 

But if you have a supplier already that you get your materials from, you can certainly supply your own and pay for labor only.

If they refuse to fix the tile then you have to hire somebody else to fix it then decide if you want to try and go after them for any cost difference which will likely not be worth the effort as it will be difficult to prove who said what and less you have everything in writing and signed off by both parties.The way to avoid this in the future is to let the sub contractor supply the material and or make sure you have a detail submittal signed by both parties of what goes where and make sure everyone knows not to install any tile until either you or someone on your team can be on site before the tile goes down to make sure everything is in the right place. 

@Greg Ghunt, how smoking hot is this deal?