I don't think it's legal at all. If you're making official pricing recommendations, you're essentially trying to convince competing businesses to agree on price

I don't think it's legal at all. If you're making official pricing recommendations, you're essentially trying to convince competing businesses to agree on price fixing, by definition. It doesn't really matter how you arrive at that recommended price. The only way this could work is if you give individualized pricing recommendations based solely on public information + the information of the specific landlord, and if your marketing and contractual agreements and so on make it very clear that different landlords will see completely unrelated prices. Otherwise, even agreeing on the same pricing formula is an illegal form of price fixing (say, if everyone agrees to sell at public average price + 10%, dropping down to public average price + 5% if unoccupied for one month), per the FTC briefs.