You need to look at what you are getting from the builder and compare it to what you are paying. If you are getting advertisement space, and you are paying a reasonable price for it, then you don't have a section 8 violation. This scenario is specifically addressed in HUD's FAQs for industry.
"18.Can a mortgage banker and a real estate broker advertise their services together, for example, on the same brochure or newspaper advertisement?
"Nothing in RESPA prevents joint advertising. However, if one party is paying less than a pro-rata share for the brochure or advertisement, there could be a RESPA violation."
If you are getting advertising and not paying for it, or paying more than your share, then you have the presumption that the compensation is for referrals.
Opinions are mine and not necessarily my employer's.