I do about the same number of rehabs you do...about one per month, on average.We use the same two crews on everything as well, but they don't include a GC and don't include some specialty trades, such as:- Licensed Plumber- Licensed Electrician- Licensed HVAC- Cabinet Supplier/Installer- RooferSo, we use our main crews for about 80% of the work, and then also have to schedule and manage these other specialty trades.

You could also call some of the national carpet suppliers like empire or national floors to see what they'd charge. 

Try to find some slab granite pieces in the boneyards of the suppliers.

For contractor references I usually find its best to go to your local building supplier and ask who they recommend. 

tobonsai.com  -  Haven't tried them yet so can't give a first hand review, but after listening to the owner interviewed on a STR podcast it seems that he has thoroughly vetted suppliers to get a good product to STR owners.

Scott;1st always use the KISS approach to any project or deal, the more complicated you make it there more complicated it will be.I have built for investors, custom homes and specs, all different in there outcome of how profit ended up.Get three bids with their schedules and there plans, this will give you an average, call there references, I mean previous homeowners that the bidders built for, pick up the phone and call some trade’s, the construction business is a small world all the trades/suppliers worked or knows somebody that have worked for the GCs.As for what to payout would be, my rule of thumb is, cost to build x 25%, the 25% covers my overhead, taxes, legal fees, mister Murphy ECT, then I verify that number with a CMA from a Real estate Broker, if numbers line up then where good if not the adjustments will be needed.

That being said, smaller local suppliers can beat them on service if they are good.

I found the deal through SIDRAN wealth a turn key supplier that develops homes in secondary markets.

Contractors want to buy the materials because we have relationships with quality suppliers.

I interviewed several solar companies before I went with Revolusun in Burlington MA.Mass electric announced rates to go up again because the suppliers providing power to national grid rates when up.