Problem with playing B&M $1-2 NLHE for a living is the speed of the game is so slow you cant get the hands you need. that being said I still think IF you had to you could make a living at this game BUT you would have to play solid hours 5-6 days a week. I think you could net $150 a day or around $750-$1000 a week. Your ability to consistently earn money in slow B&M games is that your opponents need to play poorly ...so game selection is everything. Do you really want to sit in the Commercre or Bike or any Vegas pokerroom for 6-8 hours a day 5/6 days a week...B&M pokerrooms are disgusting after awhile...you can do it online much easier.

For a starting bankroll you need at least $3K plus 3 months expenses ie another $5K++ if you dont know what the heck you are doing or you run bad.

Ssems to me B&M games thu the opponents in general may be more live than online players ..the game may play bigger with the bigger pre-flop raises..this menas higher variance.. I would definetly say 20 buy-ins is a minimum. Really matters how you do when you first start..if you run crappy and lose 10 buy-ins your first week or 2 ..will your wheels fall off? Having a bigger br will make it easier to stay level if you get off to a bad start. Good Luck..If you find the $1-2 games easy ..try moving up to the $2-5's methodically.
I would say you need a $4-5K starting bankroll another $5K for backup expenses. If you know you can beat this game for a living you could start with as liitle as $2K/$3K.