«Со» is a form of «с» used before consonant clusters. Usually it's optional, but before «мной» it's required (and other cases starting with мн-; also before всё 'everything', все 'all').
Other prepositions also have such forms: с/со, в/во, к/ко.
You sure are a helpful frog. I see you more often in this course than the real moderators (the ones with a tag).
Indeed, corrected. Thanks!
Is this work on tidying communal areas (e.g. snow-clearing) or could this be any task that is done outside (not necessarily public areas)?
The latter. It doesn't neccessarily mean tidying communal areas. It can mean e.g. working on your own house too.
In case any nonnative English speakers are lurking: be careful translating "in the streets" or "on the street" literally into English—for some reason it is often a euphemism for being a prostitute (of the "streetwalker" class, not in a brothel):