Your BartAccount
When you join, your BartAccount will be 0. You have nothing to spend. And you can't exchange any other currency into Barts. Not to worry, we allow you a free overdraft. Limits are set from time to time, to avoid abuse, but in general, it isn't a problem. After all, isn't the lack of credit the reason for the problems in the economies of most countries in the world? So why should we strangle BartLand!
And on the other side of the coin, is the Bart Millionaire. You could amass so many Barts in your account, by not spending them. But if you do that, you have completely missed the point - it's about bartering, the benefit comes when everyone passes on their skills, and whether you are planning to do babysitting or brain-surgery, it's the same thing.
Remember the 80s? "Greed is Good" was Gordon Gekko's catchphrase in the film, "Wall Street". Here in Bart Street, "Spend is Good". OK, not quite as catchy, but definitely a lot more sensible. Because when you spend, you get the benefit of other Members skills. And they in turn can enjoy the benefits of yet more Members.