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.