As noted, he was a
flaneur, which would fit in the artist scene. In the US he might have been seen either as a "gentleman of means" or someone "with no visible means of support". Today he would be considered in the gig economy--still a fringe position for some.
Comments on getting up early to avoid the crowds...I don't think so! Then, now, except during plagues and invasions I doubt there have been empty streets in Paris, since there have been streets in Paris.
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This and others show the ghost images you would expect, glass plates and slow lens in a dusky street view... and if you look at this gallery most (or so) show people, in anything that shows more than a half-block of a street.
A lovely slice of Paris in time and space...I need days to look through these for familiar places! My memory of Paris in the '70s is closer to some of these than to 2024--that's a scary thought!