the income taxes you would owe to Ca is based on your total taxable income there not just what the sole proprietorship earns. the same rule appies for federal purposes.
if your only income was the $700, then for federal you would owe about $100 in self-employment taxes but there would be no income taxes. with taxes that low no estimated taxes would be required.
for Ca with only $700 in income you wouldn't even need to file a return.
apparently, you are providing incomplete information. the top Ca tax bracket is over 12% but you need over 1/2 million $$ in taxable income to be in that tax bracket. where did you come up with 15%?
