Car engine corrosion?

I'm looking at a car for sale. The body, under carriage, and interior are very clean (2000 Camry with only 97,000 miles). It's from Minnesota, now in Calif. It seems to run great, smooth, shifts fine, everything works etc. I'd make an offer except for one red flag.....The silver metals including some parts, nuts and bolts under the hood have very obvious surface corosion. Is this a reason not to buy? I'm afraid of the extent of the corrosion and don't know if it's just on the surface or can it get in deeper and cause problems?