What exactly is a “rehoming fee” for adopting a pet from someone? And what’s a reasonable rehoming fee?

Someone asked for a $300 rehoming fee for their puppy…is that unreasonably high or fair?

I thought of adopting a pet for someone as a gift, but I’m reluctant. What do you think?

Someone close to me keeps stating they want a cat or dog, so I thought of buying one as a present. Is that appropriate? Would it be best to take the person with me? Or maybe just buy something else as a present. People change their minds, and I’d hate to buy this pet and the person not take care of it.

What types of questions would you ask for someone adopting your pet?

I am moving and have to find new homes for my two cats. Please don’t write me about me keeping them and/or being a bad pet owner because I absolutely can not keep them and yes I hate it.
Anyway, I put an ad out on this Vegas website asking for people to please adopt one of the cats. I am offering a cat carrier and $30 Petco gift card with each cat adoption. The only thing is I want to make sure they are going to good homes without ulterior motives.
What questions would you ask people to ensure this?
Thanks!