What was Marie Curies first job?
This looks to be the answer, taken from Wikipedia:
Maria made an agreement with her sister Bronisława, that she
would give her financial assistance during Bronisława's medical
studies in Paris, in exchange for similar assistance two years
later. In connection with this, she took a position as governess.
First with a lawyer's family in Kraków, then for two years in
Ciechanów with a landed family, the Żorawskis, relatives of her
father. While working for the latter family, she fell in love with
their son Kazimierz Żorawski, which the future eminent
mathematician reciprocated. His parents, however, rejected the idea
of his marrying the penniless relative, and Kazimierz was unable to
oppose them. Maria lost her governess' position. She found another
with the Fuchs family in Sopot, on the Baltic Sea coast, where she
spent the next year, all the while financially assisting her
sister.