what is the minimum budget allowed for adwords?
There is really no minimum or maximum.
I have seen campaigns set as low as .50 daily... and heard of campaigns set ever lower. Please keep in mind you are not going to see much (or really any) performance for a daily budget like that.
Please keep in mind that AdWords works from a monthly budget formula of 30.4 days X daily budget. Use it to determine what you want to spend per month... and plug in your daily budget and off you go.
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