What type of cladding does it have?
Get a professional to go through the books and the OC minutes to see what problems have been raised and how they're handled.
Are the levies appropriate? Too low and there isn't any money for long-term repairs.
How much money is in the sinking fund and what items are listed to be addressed in the next ten years?
What long-term contracts has the OC entered into?
Do they have any embedded contracts for utilities such as electricity/internet?
How long is the term for the Strata Manager?
How are renewals handled?
Is there friction between residents? What form is it taking? You don't want to walk into a Hatfield/Mc Coy type feud.
How many apartments are let on the short term market, AKA AirBNB. What trouble does it cause, especially on weekends and public holidays?
Is the maintenance up to date? If there are lifts, are they up to standard with a maintenance plan? When are they due for replacement?
These are the basics, there are thousands more to ask and ensure you get appropriate answers.
Good luck.