Cons: paying union dues when not in the union, paying for insurance that you can't use
Don't even bother. You'll get minimum wage, get minimal hours, pay union dues, a union 'initiation fee', and pay for insurance that you'll never be able to use.
When it's all said and done, you'll get less than minimum wage.
The union, UFCW, is beyond useless, and only exists to suck money from your meager pay.
Don't even think about doing this to supplement your income, but again, it's not worth it.