[Qgis-user] Combining modern maps with old maps

[Pathin]

Hello guys

i am a private researcher who is analyzing where some former old 
buildings has been
most surely been located.
For that of course i have sometimes just a very old map (sometimes a 
picture or a scan).

How would be the best way to "overlap" this with a modern map like OSM.
I am sure i have to create two layers and the layer for the modern map 
is easily to do
with the plugins.
But how to process the "old" map the best way: would do you recommend to do?

many thanks

pat