If he was paid in rubles, I assume it was USSR or Russia/ Belarus after USSR collapse? I personally find it quite hard to believe, unless he is old enough to have lived before WWII. Or if he just went along to help his family and was given some pocket money.
During the end of the Khrushchev years. As I posted previously, my husband is from Ukraine. He and his cousin, who was 9, worked for a man who sold chickens at the market. The man didn't need the job, he just enjoyed it. Both my husband and his cousin came from an "undesirable" class (parents were non proletariat), and therefore, they were dirt poor. In the so called "egalitarian" socialist USSR, they both also were underfed, so from that age on, they hustled for money. My husband also used to catch fish and sell them for 2 rubles outside the metro station. Money was always incredibly tight, his avenues to higher education were blocked, and he had to take a job that was usually a pathway to live in the city for escapees (peasants from villages), as he lived in a closed city.
Choose to believe or don't, I don't really care, but it's all true.
@Rezie, when I was a child, latch key kids were common, but we also were dirt poor, so there was no choice. Children that age walk home alone now occasionally, but most are bussed or driven to and from school. But social services would be called if an 8 year old were home alone.