Reading the OP's posts here, I get the impression he kind of has his mind made up: He is trying to find a nice way to explain these guys why he may just no feel so comfortable to do this.
Well Sir, If you are experiencing difficulties to say "NO" plain a simply, I don't think that the loan biz is for you. It takes a very decisive and self centered state of mind to play loan shark... ANYWHERE... but especially here.
I mean what are you going to do not to fear to offend this people when they will start to serve you all sorts of heart breaking stories... in monthly installments instead of your interest bearing payments?
I know people who do this, here, elsewhere, anywhere. Successfully too. But they will not be bent any which way. That's not the kind of people they are. If they feel not 100% in control, they won't do it... and will just say NO.
Believe me, that it is not my intention to offend you in anyway, but from your initial question and your posts here I must say, I believe you are not that kind of person, so, don't try to play it.
So, if you want to place money at high rates... find somebody who is experienced at doing it or just tell you friend's friend you will NOT do it, period. Don't even say you are sorry or make explanations as to why not, it will only make them come back with new stories.
If he doesn't accept your "NO" and keeps calling you to tell you all sort of new stories... you will have a taste of all you would have been faced with, would you have given in.
With money, you don't give in anytime. You do what YOU want only, at your terms. Always, or you will be taken as a sucker.
... J-D.