#2. Old Wiring or Plumbing
I'm lumping both of these into one the issue because usually if the wiring is old, the plumbing is as well. If you have a historic home, and many neighborhoods around Portland of homes at least 80 years old or older, you could have the issue of old electrical wiring or plumbing. Again, a home inspector will be able to tell you about the age of the wiring and its potential problems. If things are not up to code you might be in for a rude awakening. Replacing wiring or plumbing can be extremely costly, but, it will definitely increase the value of your home by having these two major items updated.
Buyers just don't want to inherit plumbing issues or old wiring problems. If you've never had a plumber look at your pipes you may not even know that you have aged materials. Clay pipes are particularly vulnerable to tree roots and any damage to these type of pipes can cause significant damage and plumbing issues later on as well. It might be a big hit, but if you're planning on selling, plan on updating the plumbing and the wiring regardless.
Additional: Rochester MI Realtor Linda Abraham says: Knob and tube wiring or lead pipes are a huge issue and one that should be fixed. Homeowners don't like it and many will try and sell as-is but low-ball offers quickly make them think about it. No one wants to buy a house with $10,000 worth of repairs right off the bat unless you're an investor and then, you're not paying full price. IT can be a costly hit but well worth it in the end.