If the benefit is going to the purchaser, no issue. If it is in any way indirectly benefiting the builder...then you have a problem, in my opinion.
This could be looked at in either direction...since, at least in our market, the seller generally pays the majority of closing costs. If it were me, I'd run it past my regulator, just to be on the safe side.
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My opinion only. Not legal advice.
Say you'll haunt me - Stone Sour