How would you price before and after content at $600 a listing?

Two a month means one a month. Assume that with any referral promise and you won't be disappointed.

The thing you're actually selling here isn't the video, it's the before. Any photographer can shoot a finished kitchen. Almost nobody has the framing and the demo footage, because you have to be there in week two to get it. That's a real moat and you should price it like one. I'd say yes at $600 for the first two and tell her plainly it's an introductory number while you learn her clients' timelines.

Scope creep warning, since it's my whole personality. On your own job you shoot when it's convenient. On someone else's, the studs are covered by the time they call you, and then you're doing a second trip, or worse, you're standing around while the painter finishes the trim you need in frame. Write into the quote how many site visits are included and what a re-shoot costs. Otherwise $85 an hour becomes $40 by the third house.

Get the usage terms on paper before the first shoot. Who can post the footage, for how long, and whether the flipper client can hand it to a different agent next year. Also whether you can keep using it on your own page, which you obviously want. These are ordinary contract questions and a one page agreement handles them, but the default when nothing's written is an argument later. On the licensing question, whether video production for a broker triggers anything is a state real estate commission matter and the answer varies by state, so ask her broker to point you to their rule and confirm with someone licensed in your state rather than taking mine or hers.

@fathom is right about the broker piece. Practically the way it works most places is the broker owns the advertising and has to approve it before it runs, so your video is her problem to clear, not yours. That does mean revisions. Build in one round free and charge for the second, because a compliance edit is still an edit.

$600 twice a month is $14,400 a year for maybe 170 hours. That's real money if it's steady and it's noise if it isn't. I'd want to know whether she's the only source. One agent as your entire client base is the same risk as one tenant in a building.

I'd take it and stop analyzing it, which is rich coming from me. But do one thing first: shoot the next house on your own list as though it were a paid job, with her timeline and her deliverable spec, and time yourself honestly. Then you'll know if seven hours is real or if it's seven hours because nobody's waiting on you. @harrow's second trip is where the number goes wrong.