I had an inkling about being able to get a court order allowing you to garnishee the rent from the property, so I’m glad to see our legal eagles have confirmed this possibility.
As for costs, I believe the reasonable costs of recovering strata debts can be added to the debts themselves (check with the lawyer you will need to pursue this).
And in the meantime you can get a strata loan to allow you to hire the lawyers to get your money back.
I’m curious to know why your strata managers didn’t suggest this to you. In the meantime, if you can only recover the last six years’ levies, as suggested above, then you have effectively given the slack owner a 40 per cent discount. Ouch!