How old is too old for a rental?

[Patrick Zwierzynski]

When starting out in looking for rental properties, most people recommend that you come up with specific criteria so that you can quickly identify properties that would be of interest. This process seems pretty easy to me EXCEPT for determining if the age of the home is an issue. So, I wanted to get input from the BP community, how old is too old for you? Or does the condition of the house mean more than the age? I live in an area where a lot of homes are older, and buying a home built in the early 1900's is a little scary to me. You never know what is behind the walls. Any input into your thinking about this would be of much help! Thanks in advance.