Previous 2 family was converted to a 1 family

[Walter Correia]

I found a 1 family home at a discounted price in a decent neighborhood. The home was once a two family but the owners converted it to a one family and are selling it as a 1 family. After seeing the house I noticed that no walls were moved. However there were some door ways made to make it mor efficient as a 1 family. My wife and I put in a offer and it was accepted. The reason why we pursued this home is to converted back to a 2 family. What should We do before we sign a purchase agreement? Why is the process of converting this property back to a 2 family? Thank you in advance!