(Currently our rebar supplier is behind 2+ weeks and these materials were ordered 45 days in advance). 

They don't rely on ONE supplier, ONE broker, ONE anything.  

Not to say that you'd pick crappy materials, but contractors with experience have manufacturers and suppliers that they know guarantee their products and that helps them know they can stand behind their work. 

I get that there are delays and behind the scenes, dealing with late suppliers, the city authorities being difficult, but I thought for sure I would be further along than this. 

And all suppliers and subs are current as is the customer .  

Continue to expand my vendor/ supplier relationships for my construction companyIs the school near Philly? 

You have suppliers (roofstock), employees (property manager), and customers (your tenants).

I found through a referral a great supplier that can provide new, and not scratch and dent, for about what I would pay for used.

If you are the lone supplier of a specific housing product and there's pent up demand you will absorb your units quicker and have tenant stay longer given the lack of alternatives.

Plus, building those relationships with contractors and suppliers while gathering numbers can lead to better deals down the road.