Your building’s DA would have stipulated a number of visitor parking spots as conditions of it’s approval – Council may not like you turning them into extra spots for tenants, especially since there may have been deliberate decisions to limit the number of car spaces available to residents in strata (to get us to use public transport more).
Owners Corps can rent out common property and the money goes into the admin fund. However, I believe the tax office views that as an earning by the individual owners who have to declare their share of the income in their annual tax returns.
A better way to solve the problem and make some money would be to padss a by-law allowing the Owners Corp to impose an administration charge for the pursuit of Notices To Comply. You can’t fine owners directly for breaches – but you can get owners to agree to cover the cost of taking action agains owners when breaches have been notified.
I hasten to add, the legalities of this are pretty dodgy but it is a wonderful scare tactic if you want your visitor spaces to be kept for visitors. Even without that, tenants should be reminded that by breaching by-laws they are breaching their tenancy agreement and could then be evicted.