~snipped~
And before then as I said, tell the person both the pros and cons so that you not be held responsible when there is any downfall.
Experience has taught me never to trust people for their verbal agreement when it has to do with a huge financial commitment. Not everyone can take the hit when shit happens. Some will melt under the heat and deny they ever agreed to it. If you must go ahead with that, try have some sought of cover for yourself; either as signed agreement or audiotape it. It's just an honest suggestion.
Make person nor carry you enter police station.
Always give a disclaimer that no matter what the results will be is that you are not liable with the consequences that they will face. You can always give your inputs but it doesn't mean, they need to follow. At the end of the day, it is their money at stake, so they need to take care of their own funds as no one will look for it but themselves.