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If you are willing to work during your studies to cover some expenses, the best way is to look for b-schools which provide graduate assistantships. This is work that you do for the b-school and you get paid for it or have some of the costs covered by the assistantship. These opportunities are limited and you should meet professional criteria to fulfill the job provided by the assistantship and maintain good academic standing.
It is not recommended to rely on a part-time job if you study in a full-time programme. MBA studies are demanding and highly intensive and it is not realistic to combine work and full-time study.