I don't know what this site is. What's P2x?

Oh so the x stands for "either P and/or B", I get it now, thanks. My first question is I'd like to know what platform could be used for parties who already know each other. By waiving my right to be helped with collections (and certifying I take responsibility for the risk of loss), I'd like to for instance loan $1000 to someone, without either of us ending up paying for things we didn't need (like finding each other in the first place) or don't care about (like credit checks/reporting and such). And where I can choose what the interest would be, or even to make it zero. I just want a way it can be official in some way, like posted online on the Internet somewhere, as a record, of the person not yet and then having paid me back. Where it goes through some site like with PayPal, so that there's no chance of someone forgetting what they borrowed or that they haven't yet paid it back.

Sounds like you just want a private contract between the two of you. I expect there are sample contracts online somewhere you could modify, or go to a solicitor, although that might be too expensive, as michaelc implied I don't think there is anything like that out there on P2P.