Maybe you can tell us what P2P platforms you mention, so we can check it by visiting the website. I don't invest in those platforms because I don't have much information or data to select which platforms. But I don't think that the returns will be high as you say because if the return is high, you really need to be careful. After all, that will be too good to be true.
For legit platforms, the returns wouldn't be that much but you still going to have gained from it. Until now, there's no reply from OP and I'm not expecting him to return and answer those questions that we have for him.
But the idea that he has brought here is a very nice idea for those who are looking for additional sources of income.
I have been recommended to look into MINTOS. It is a sort of a marketplace with over 80 different companies selling loans, not just one chosen by this company, but many with thousands of loans. So it is seems it possible to diversify the portfolio very well, so it could be maybe safe? It is also written there are loans with money back guarantee - is that possible? They claim to have 14% return. Anyone heard of https://www.mintos.com/en/