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This really depends on your accuracy requirements and the intended purpose of the georeferenced map.
You can georeference any map image to a basemap. The result will end up with the spatial reference of the World Street Map basemap. Which may or may not be appropriate for your intended purpose.
If you are after accuracy then you will get better results using other basemap data such as a road centers or a land parcels. It depends on what features are in your overlay map that you can use as georeferencing control points. Ideally, your overlay map and the basemap have shared features that can be used for control points.
I am hoping to use ArcGis Online to show how the area has changed over time
In this case then it is probably a good idea to use a basemap with the same projection as ArcGIS Online - such as the World Street Map. That way no other re-projections are required.