mold in the basement questions

[JD Mims]

Hi all. I am purchasing a duplex that has mold in the basement. 

I sent out a contractor for evaluation and came back as- only mold in the air in the basement. 

Contractor said it wasn't 'old mold', it was 'new mold' and he felt like it was mainly because house had not been lived in recently and could be fixed with bleach, ventilation and circulation.

How will I do ventilation and circulation?