Note:  LLC has bought/sold $12 million over the last year with and made a profit of 650,000 (without any of the partners RE commission contributed to the profits)Going forward Partner #1 wants the RE commission to be included in the profits - less a flat fee to her.   

With the 2 and 3-flats, you're at the mercy of comps, which is pretty much pure speculation.

I have a 3-flat and a condo.  

So now when they travel to Paducah KY for their kids traveling sports tournament, they are searching out Airbnb's instead of the Hampton Inn, in a town no one thinks of as an Airbnb hotspot.For work travel I'll stay in a hotel, but for ANY and ALL family travel, there's no way I'm giving up having a separate room for each of my kids.My mountain market revenue is flat-ish to up, but that's because I took over management from a PM and was able to do a much better job, so it's hard to get a pulse on my local market.

On a few occasions I negotiated a flat rate of $4000 because brought the buyer and just wanted them to do the paperwork.

FHA will also not loan on the house mentioned above because they estimate that the repairs could be in excess of $5000.

As Don mentioned above 20% or less of equity in a market that is flat or falling is NO equity if you need to exit.

Anyone with access to excess capital and credit can do better on their own, and anyone without those things should be very careful going all in with their savings on something like this. 

Is there any precedent for realtors or other placement services charging a flat fee instead or half month rent?

After the market crashed in 2008 we went on a buying spree from about 2009 until 2015/6 (buy & hold) until the numbers didn't make as much sense as the prices started creeping up again, rent prices were flat and many competitors started entering the marketplace.