Thorns,

You can bet on the TAB [s-tab anyway] for as low as 50c. as long as they are on-line bets so you would need an account. Alternately those auto-bet machines at pub tabs. etc. also allow 50c bets or can be used to deposit cash to your account.

I have often used my TAB account and 50c bets to do real-time trials with systems. Not the best odds but credit facilities are not required as deposits [and withdrawals] to an account can be made at any pub tab. Serious betting can always be shifted to Betfair or IAS etc. at a later time.