It's not as simple as having X buyins. As a pro, you have to factor in that you'll be taking money out of your roll to cover your living expenses, and this will happen whether you win or lose. So while you should start with enough money set aside to cover your expenses for at least a few months without dipping into your BR, that just delays the inevitable since it will get used up unless / until you replenish it from your poker BR.
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also adding to this, mixing game speeds is difficult. they each require slightly different skill sets in order to achieve good/great results.
its best to master one format, and then move on to mixing different game types.
also, google an expense report. make sure you put in correct figures, and make sure you actually put more money than you think you will need, like, if rent is 150, put 170 just to be on the safe side. once you have a monthy or weekly goal, you then have a starting point for how much money you need to make per month, or per hour to achieve your goal.