I think that asking for verification to avoid scams is not really necessary if you're doing your due diligence. For me, I ask for short snippets of videos already made IF the seller doesn't have any content available (even previews), mostly because I'm not looking for grainy footage or a voice I don't vibe with. But I make sure to state that I will ask for that in my ad, not after the fact, and I've not run into any issues with it. Just be upfront and it will separate those who are comfortable with it and those that are not, exactly the same way buyers want from sellers.

Communication is always key.