I vote for zero...in the words of George Michael, "Sex is natural, sex is good, not everybody does it but everybody should"...whoops, just came up with a prerequisite: Both agree that there are no prerequisites.

I voted for the things I think everyone should verify before having sex with someone, as they’re a matter of safety (stds and criminal record). I would also add “consent” to the list. .

Personally, I would also be concerned about compatibility but that’s for me. Oh and relationship status - with me and if there’s anyone else.

You forgot :
Green Card
Birth certificate
Alcoholic
In the closet

??

Just make sure a condom is available. The rest will work it's way out if a relationship expands into it.

Just saw the results so far, and read the nice comments. Thankfully, we all have different opinions. Shows some security in expressing honest feelings. The most popular choice was the last one. I guess it's depending for most on the goal. Whether or not commitment is wanted.

There was a time in my life when "having sex" = "planning to get married forthwith" and so all of these issues would be in play. Sex was a Big Deal that you only embarked on when fully pair-bonded and planning the rest of your life together. In some circles you only embarked on it (or admitted to it anyway) after fully married.

In truth the last time I had sex for the first time with someone (the someone who ended up being my now-wife) the prerequisite was no STDs, general sense of compatibility and at least provisional commitment I guess. I'm still old-fashioned enough to not be into one-night stands. But this was our first physical meeting after a LDR consisting of a couple hundred hours of phone calls, emails, and texts and lots of planning, and it probably was a sexual compatibility assessment as much as anything. The list seems way overdetermined for most people today.

If you are talking about an actual long-term relationship, then all of them.

If it's only sex, then just "general health and diseases like stds"