Make sure you do a good job screening the tenants.

Also, if you want to run a reputable business, the screening process for t/b's should be thorough.  

The 3-flat didn't work out--waaaaaay more work than the pics indicated but I've found a SF that's just as interesting.

There are some brokerages that do a flat rate fee rather than a split, but you better hope you never get into trouble because they WON'T be there for you, or even be there for you to ask questions.

If you have none of this, 1) you could still be required to refund their security deposit when they leave, whether or not the owner transferred it to you, and 2) since there is currently no written lease in place, you could require screening, credit and background, employment, etc., as if they were new applicants.  

I've begun earnest research in how to screen better residential tenants, and attracting commercial tenants, which is a fair bit trickier.I also own and rent out a cottage with horse pasture acreage, although I'm mulling over offering it as a lease option agreement.

It's usually best to convert the fee to a % of the sale price as a commission or charge a flat fee as a Realtor, disclosed to all necessary parties.

Have you looked at @Brandon Turner 's "Tenant Screening: The Ultimate Guide"?

The mention thing is a little odd because you do have to know to look/scroll down the screen to see the names pop up.Message someone by going to their profile.

But if we have a flat lot with normal set backs we buy off the shelve plans all in for 2 to 3k.