Value of 19th century paintings?

Some years ago I was in Mexico and ended up for some reason in this run-down old mansion where the walls were lined with 19th century paintings. There were a lot of portraits, and also paintings with mythological or religious themes, and a couple expressionist paintings. I wouldn't say they looked like world-famous art but they were attractive and highly competent. How much is stuff like that worth? I was just curious for some reason. The owners seemed to be from a decayed formerly rich family...they were renting out rooms in the mansion to people.