(I'm not sure if this is where this belongs, so if I need to put it in a different board please let me know.)

I had a question pertaining to self employment taxes. My husband works full time making around 150,000 dollars a year. I am currently unemployed, but have been looking at getting into Amazon Mechanical Turk which is a crowdsourcing company. I have researched and found that this would be considered self-employment if I plan on earning over 400 dollars a year, which is my goal. The only concern I have is with self employment taxes. I have been reading that these taxes need to be paid quarterly. I'm not quite sure how to figure out how much I should be estimating my income to be and am also wondering if my husband's income in any way affects the amount of taxes I would need to pay. Just as a rough estimate we'll say that I plan on making 500 dollars quarterly on Amazon. I've looked at the IRS website and it just confuses me even more. We plan to file taxes jointly (next year when this would come into play) and we are wondering if the incomes are taxed at the same rate. Obviously if we're going to end up just using all the money I earn to pay taxes I'm just not going to do the Amazon position. Any help that you could provide would be greatly appreciated.

Thank you, Jill