depends if you are going to train it yourself or send it to a trainer, I would think that a trainer is well within thier rights to ask for 50-60 per week, however this is trainer specific some will do 50/50 deals on prizemoney with no other costs.
If you are to train it yourself I would think it will cost you $100 for you licence, up to $500 for a single kennel, $100 for neccesary start items (muzzle, lead etc) and more items will become neccesary over time. Then food should be approximately $20 week or so, (4kg Beef mince and choice of $30-40 biscuit).
As for how often a dog can race this depends on the dog, I think once a week is safe, twice a week would be an occcasional thing, however some dogs thrive and love running twice a week.

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