Skittles, the "preferred lender" term makes some people nervous because it sounds like an endorsement (or, dependent upon who you ask, is an endorsement). This can create problems if you have a more in depth marketing relationship, for example if you are paying for the opportunity to be "preferred lender" or if "preferred lender" comes with perks like being included in sales contracts.
This is all in the context of RESPA Section 8. I suspect some lenders believe that using the "preferred lender" term invites additional scrutiny and they may be correct. I don't know the depth of what this relationship might look like but look into Marketing Service Agreements and the CFPB's "guidance" on these types of agreements so you can see the red flags.
Placing flyers in model homes is pretty common as there tends to be foot traffic.
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Opinions expressed are my own and do not reflect legal advice or the opinions of my employer.