I recently  worked with the one brokerage and it was the best experience I have ever had.

If his real estate business is brokerage for home owners buying and selling their primary residences, then he probably does not have the knowledge to help someone invest in real estate.

Best brokerage hands down!!

Hopefully your sale concluded with no hiccups a long time ago.Still, I didn't see anyone really address the questions and since I'm here, I'm the broker for a "flat fee" brokerage, and I have a few minutes so I thought I'd clear the air (responding to your post will shake some cobwebs loose and help me generate some new content for our website too, so there's that).

This is correct--save that an ethics violation can cause an agent to lose it's license and a brokerage to risk the same for employing that agent.

Is it allowable for an unlicensed “property finder” (unconnected to any brokerage) to charge tenants large commissions to find them luxury homes to rent? 

I have owned 3 different RE brokerage companies over the past 40 years and that's the stat's for AGents coming in to the business 10% will make a darn nice carrer out of it another 40% will do Ok and keep at it on and off over the years the rest come and go..

Brokerages can list it on their websites.

It is a real estate brokerage

If you are looking to wholesale yourself, there are barriers to doing it with a license as the brokerage must be compensated on all deals involving real estate per your license.