Qustion on referals

Qustion on referals

I have managed to find some investors / buyers that want to work on a referal. My question is if I send the investor a referal agreement and he / she signs off then I pass the information off, How do I know if he / she buys the property ? or am I going about this wrong ?
I know if I do an assignment I lock it and have control of the property, but I am not locking referals so I need away to be able to track it.

Thank you
Rocco

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