Get the Serial # to verify that it IS made in 1919 and you can also see what model Singer is it. Some go for more than others. Also, check if there are attachments and a manual included. This increases the value. Also, check the wiring...there was no power cord shown in the picture.
Also, make sure the cabinet is in good shape and doesn't need a lot of repairs.
Depending on the model, any repairs needed do add up and that is a factor in deciding if the price is good.
When you go to see it, sew on it to make sure there aren't mechanical issues. Take fabric and thread with you, take a bobbin after you verify what kind it uses.
Didn't want to scare you away from it; just want to make sure you get what you want at a reasonable price.
HTH