53 year old duplex, too old as an investment?

[Ally Kumar]

Considering a duplex that is 53 years old, has not had plumbing or electric upgrade. Recent inspection provided by seller indicates minor issues with plumbing and makes note of older electric. Needs a new roof (that was factored into numbers). Numbers work. Its a fair deal not an awesome deal. What are some of the things to consider with older properties? Something to stay away from? What is considered "Old" in real estate world? Pl share your experiences.