Possible Mold During Inspection Period

[Mark Koontz]

Hello all, 

I am new to real estate investing and have been educating myself for the past year or so and decided to finally pull the trigger. After looking for a bit, I found a Duplex that will cashflow pretty well. I put in an offer on the house and it was accepted. I am now in the inspection period. 

An inspector went through the house and everything looked good (for being a fixer-upper). The only thing that is alarming is a wet spot beside a window. I sent a picture to a friend who used to work with mold remediation and he said it was consistent with mold. I have looked at getting a mold inspection and they are a little pricey. I am not concerned with replacing the affected areas myself(as long as it is not super extensive). I realize anyone reading this does not know the entire situation, but I am looking for a second opinion - if you were in my shoes, where would you go from here? 

Thanks in advance!