There is no minimum budget for Google Ads. You could create a campaign and set a budget of one dollar per day if you wanted to, and Google will try to steer around that one dollar budget. Generally, I recommend at least $400 for the first month maybe 1 to 3 months as a test to find out what your lead cost is going to be and see if it’s actually going to be profitable for the amount you’re spinning on ads versus the number of new sales or customers that you get.