Flynn worked for Royal Trust Company in Dublin before he started selling furniture, bottled gas and drapery.
[20][21] Flynn met his wife Margaret (née Fitzpatrick) in the 1980s when she applied for a job at the Mace convenience shop he ran in Ringsend.
[8] During the occupation of Apollo House, Flynn provided mattresses to the homeless people occupying the building.
[25][26] As part of his business, Flynn has run the Mick's Community Chest initiative, which donates a sum of money to a charity every month.
[27] Flynn endorsed Jennifer Carroll MacNeill during the 2019 Dún Laoghaire–Rathdown County Council election.