Depending on your option (pre/post pay) Google says: Obviously with Pre Pay you need to keep money in the account in order to run your adverts.
Post pay you get billed every month and in prepay your ads run till the time you have funds... you will get a detailed bill report every month
Not really - with post pay you are billed in certain cycles as I outlined in my previous post. If you go over the £500 limit (as is the maxmimum) then you will be billed. Basically, if you spend enough within the given time periods your payments will go: £50 £100 £200 £350 £500 £500 £500 £500 ... ... If you accrue less than £500 within one month then you will be billed at the end of the month. Post pay - keep money in there and your adevrts will keep running.
I think you are living in Australia, so both prepay and postpay is available to you. some countries have only option of postpay.