Interesting assumptions you all make...but if you refer to the recently introduced National Credit act, you will know that by law any company offering contracts have to vett you and offer the customer some sort of protection. In addition, the company offering the contract protects itself and prevents from getting into legal trouble with the Credit REgulator for wreckless lending...
Read up, know the facts before making assumptions...and deposits are totally refundable providing you conduct your account in a sane manner!
The way credit works is quite complicated...there are about 300 factors that has to be considered when you apply for a contract / credit which all contribute to the qualifying score. This score for any credit grantor is determined by a combination of your history and the rules of the credit grantor.
So if you conduct your affairs well and you bank @ the right bank, earn the right salary etc. - you qualify without a hitch...but if it is otherwise then you maybe required to pay a deposit!