Finding a temp job before starting my full time work in March

Accepted an offer for a new grad computer science role that starts in March. I am trying to earn money before starting. I was thinking of

1) tutoring. putting up flyers, word of mouth, etc. would just be paid in cash

2) finding a temp job through an agency, like in a warehouse, driving a shuttle, teaching english online

would these 2 options be fine? do i have to tell my new grad employer about them? i accepted the offer a few days ago but the official start date is in march

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