I agree with DG above that there are no fixed rules.
But I think what is getting lost in the modern tech-y world is that a long and complex board package is a feature, not a bug.
When properly done, they serve to connect the buyer and the building, provide a hesitant co-op board with an easy road map to approval, and are a strong arrow in the quiver of marginally financially qualified buyers. I find them agonizing, and yet they're one of my favorite parts of the job.
That said, they are weeks of work. So I think that any agent the buyer shows up with, whether they found them on StreetEasy or in the gutter or here in the rarified halls of Urban Digs forums, should do the bulk of the heavy lifting of the application, and then the seller's agent should review.
There are agents and services that will do board package preparation only, but I think that's a "you-get-what-you-pay-for" sort of scenario.
Ali
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Alison Rogers
LIcensed Real Estate Broker
Upstairs Realty