Another possibility would be to find the commercial suppliers in your area (the big warehouses with little or now showroom that sell to HD and Lowes and the big contractors) ask to speak to outside sales. 

Offer to pay for the materials upfront (call in your credit card to the material supplier), and then offer to pay the rest of the 50% deposit (50% minus the materials cost) when he shows up to start doing the work. 

The other issues are secondary things.Shop around or ask local investors (that you meet at the REIA or here on BP) for a used(if on a budget) appliance supplier.

Also, I got the materials due to a customer special ordering the materials, deciding they didnt want it, and the supplier wouldn't take it back.

The payment would be made out to him as well and not directly to whoever his window supplier is.I got another quote from a Universal Windows who can also do the job for about $6800.

You can save money setting up contractor accounts with wholesale window suppliers, plumbing, roofing, siding, flooring companies etc. 

If they're so under capitalized that they don't have accounts set up w/suppliers, or they can't front material costs themselves, you don;t want them.

They are THE producers/suppliers/masters of their specific craft or product.In terms of RE, the tortoise wins. 

My primary job is as a project engineer, and I do this daily with suppliers and clients worldwide.2) Fly in early in September/October to be physically present. 

Most suppliers will require a license number to sell you HVAC equipment.