some things in relation to property investing are deductable expenses (intrest on the mortgage used to purchase the house) whilst others are depriceciating expenses (carpets, etc), and then there are some expenses that are deductible over a certain number of years (purchase costs, and in the ACT stamp duty). In terms of whether an expense is deductible or not depends on whether the expense is going towards a repair (ie, fixing an existing fence) or replacement / improvement (replacing an existing fence with a new one).

Get yourself an accountant who deals with property (that is important) and ask them if you are unsure.