I'm assuming this strategy should work fine because any realtor wont be able to negotiate price down with the builder (who will go with the next person on the list if im not happy with the price) Since I'm already on their priority list, can the builder refuse to pay buyers agent commission? 

Not sure about Texas, but here in North Carolina that sort of thing would get serious attention if reported to the Real Estate Commission.

Did you have a contract with the seller or did you put something in the contract stating seller would pay your commission?

They earn the commission and then they stay on and manage it.

It is not unheard of, but I'd imagine it to be a bad business practice not to allow flexibility if it spoils the deal. 2% buyers commissions in my area are very rare. most are 2.5-3% sometimes subtracting a small transaction fee (something else that is odd to some and common to others).

I found out that if i pick openlisting.com or reali (reali just has a flat fee), i get maximum returns from buyer agent commission. 

If they are unable to save you anything then you won't have to pay them as they work off of that 40% commission.

I know it could be a commission based percentage , flat fee, or combo of both.

We're looking for help for the best tax strategies and setting up entities for rentals, flips, commissions, etc...Recently got laid off of my "full time" job and I just started the GA sales pre-license course. 

Around here that commission is 6% (taken at closing).