How big is age of property a concern?

[Rajeev Gandhi]

I came across a nice duplex built in 1885. The owner has done an amazing job keeping up with maintenance. It's very neat and clean and looks very modern from inside. I thought it was 20-30 years old. It also has nice cash flow. I'm not sure if I should be concerned about the age of the property. I will definitely do due diligence by having professional do house inspection as well but I'm confused. I would appreciate any thoughts.