@riktiggutt:

Does anyone know some web-site?

How about daddyhunt.com?

@Kekkaishi:

It's actually a fantasy of mine to "forcefully" cum in someone's mouth: holding his head on my cock so he can't pull out while I cum in his mouth. but sadly, it's still a fantasy. I only came inside when it was consensual

I'm sure there are guys that would love for you to "force" them. Of course it would still be consensual.

@Kekkaishi:

Can someone please suggest a good Master / Slave gay community where you can find people for the purpose of establishing such a relationship?
i'm not talking about depiction of BDSM porn. (which I would also like)
I could only find Collarspace.

There's Recon, and also Fetlife, which isn't exclusively gay or M/s.

OK, then it comes down to how much you trust him. Do you trust him enough that you think he wouldn't lie and put your health at risk?

Is your older friend going to be having unprotected sex with other people as well? If so, I wouldn't say it was safe for you.