Pay particular attention to the strata meeting minutes from the most recent meeting going back a few years. Any ongoing problems or issues which may result in a future levy should become apparent. For example, recurring plumbing problems might be a warning that some pipe replacement might be on the cards in the future, for example.
I specialise in units and I find the meeting minutes and body corporate accounts the first things I study in detail.
A unit I recently purchased was a serviced apartment until a few years back. A Body Corp was set up but it was unrealistic. The Sinking fund had $30 in it
But a lot of work had been done (fire compliant etc)
They had a special levy last year to paint etc.
It is law now that a 10 year plan be completed. Once this is done it will give you a breakdown so a levy can be set. No-one can tell you how much it will be. It varies according to the block (lifts, pool, shops underneath etc) The owners set the levy. Make sure you attend the meetings. Get on the committee if that interests you.
Maybe look at similar blocks in the area. And look at the structure of th building. We looked at one which needed most windows replaced. BIG money.