If you sell a side project, what should you prepare before talking to buyers?

I see a lot of people trying to sell small side projects these days. I’m thinking about doing the same, because I want to focus on my main project and I don’t have time to scale everything.

If you’ve sold before: what should a seller have ready before talking to buyers? What questions do serious buyers usually ask?

Also: how much info is “safe” to share early on, before you know the buyer is serious?