70s Honda CBs and 60s BSAs are becoming collector's items, I don't think I'd want to use one for learning since damage from dumping it could drastically lower the value.
And you ARE going to dump it at some time while learning.
Starting off road isn't a bad idea, dirt hurts a bit less than pavement... a bit.
Just remember you need to be able to ride on the street in traffic as well to develop the sharpened situational awareness that will keep you alive, so something with on/off road capabilities would be a good idea.
Rule #1
When you are on a bike you become invisible to people in cars, ride accordingly.
Rule #2
See Rule #1
http://www.nolo.com/legal-encycloped...ses-30330.html
My Wide-Glide at Whale Rock Reservoir near Cayucos, that's the ocean just past the dam in the distance.
