ants- cost to fix?

[Steve Hilborn]

I'm looking at a 6plex in western Washington.  I seems to have a bit of a bug problem.  I have zero experience with bugs, but this looks pretty bad.  Can anyone tell me how big of a problem this looks like? Should I run for the hills or try and get it for a good price?  Is it likely that the entire building looks like this under the siding or are these type of things pretty localized. Help!