This question is aimed at the cash game players in particular;

When does a cash game pro withdraw money from their bankroll for living?

The best way seems to be to pay yourself a wage, typically as a fraction of your win rate. If your long term win rate is, say, 4ptbb/100, then you might pay yourself 1ptbb/100. You need to consider your risk of ruin, taking into account that your bankroll-winrate is now going to be reduced to 3ptbb/100, so you will need a larger bankroll than if you didn't withdraw, or take the additional risk of larger RoR.

How much to pay yourself is going to depend a lot on your $ requirements and how much you make.

Also, you should consider whether it would be possible to make a living if you had to move down due to bankroll size. Many pros who are already playing at the very bottom of their profitability limit can not move down, because of this, you would need to consider your RoR *given* that you can not move down.

are you a cash pro/full time player?

Most of us as far as I know just withdraw when we feel like it. You generally just keep whatever online that makes you comfortable (50BI or so for most), and withdraw over that unless you're planning to get coaching or take a shot.

No

I don't play for a living but id say what Rusty said is a good way to go, but also take into consideration the hours you are logging. What im getting at is if your paying yourself monthly, look at how many hours you played that month and pay yourself accordingly in keeping with you long term win rate. therefore the amount your taking from your bankroll will be nicely balanced with how many hours you are putting in. Hope this dosn't sound confusing?

I imagine it's different for everyone so there's no "right answer". Obviously you should take out whatever you need for monthly bills, plus a little spending money.

But also, it doesn't make much sense to leave a ton of money sitting in your poker account. So unless you're planning to move up, it's probably a good idea to withdraw a lot of your "extra money" and invest it in stocks or whatever. That's also a lot safer than leaving it in your poker account. This way you can access the money a lot faster if you ever need it.

Another good reason to keep some of your bankroll off the poker site is bonus clearing. A lot of sites have deposit or reload bonuses, so you can deposit up to a maximum amount and double that deposit with a bonus after playing a certain number of games.

If Full Tilt or PokerStars wants to match your $600 deposit (other sites have bonuses as well), it's free money. All you have to do is put the time in at the tables to clear the bonus.

I like your thinking here, but I prefer to maintain part of my bankroll on each of the major sites. This gains the advantages you describe (as I can move money from one site to the other to take advantage of a bonus offer) while keeping the money in play for both sites.

Every situation differs. Clearly, one guy who has a family to support is gonna need more money than one who doesn't. But if you play poker for a living, you should always have at least 40-50 buy-ins available (ideally, you should aim for more), and then keep the rest. If you have some other sources of income, a job or something, then maybe you can lower it to 30-40 buy-ins and keep the rest. It's all a matter of looking at your own individual situation and deciding what kind of life expenses you need covered and all that.