To renovate or start again?

[Annetta B.]

I just baught a house on a river in a small Ontario town near Kingston. It's a duplex which I was going to rent out (both sides) 

I have come to the conclusion that it needs to be gutted. I'm wondering how people figure out if it's better to renovate everything or start again. I don't thin k there is much of historical significance as there was a fire and it was rebuilt in the 40's or 50's. It seems to look ok from the side with new sideing and windows. I guess I need an inspector to look at the basement and walls?