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.

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. 

(A) A landlord who is a party to a rental agreement shall do all of the following:(1) Comply with the requirements of all applicable building, housing, health, and safety codes that materially affect health and safety;(2) Make all repairs and do whatever is reasonably necessary to put and keep the premises in a fit and habitable condition;(3) Keep all common areas of the premises in a safe and sanitary condition;(4) Maintain in good and safe working order and condition all electrical, plumbing, sanitary, heating, ventilating, and air conditioning fixtures and appliances, and elevators, supplied or required to be supplied by the landlord;(5) When the landlord is a party to any rental agreements that cover four or more dwelling units in the same structure, provide and maintain appropriate receptacles for the removal of ashes, garbage, rubbish, and other waste incidental to the occupancy of a dwelling unit, and arrange for their removal;(6) Supply running water, reasonable amounts of hot water, and reasonable heat at all times, except where the building that includes the dwelling unit is not required by law to be equipped for that purpose, or the dwelling unit is so constructed that heat or hot water is generated by an installation within the exclusive control of the tenant and supplied by a direct public utility connection;(7) Not abuse the right of access conferred by division (B) of section 5321.05 of the Revised Code;(8) Except in the case of emergency or if it is impracticable to do so, give the tenant reasonable notice of the landlord's intent to enter and enter only at reasonable times.

That has a negative effect on supply of affordable housing, and it immediately pushed rents up in saint paul; despite what that was meant to do in the first place.  

Those fittings work on practically every type of modern supply pipe, except galvanized, which requires a threaded transition.