Downsizing and worried about hidden costs

Keya Life By The Lake keeps coming up every time I shortlist something. My kids have moved out, so my wife and I are downsizing from our big house. We're looking for a manageable, low-maintenance flat. A big concern is actual society maintenance post-possession. Builders often quote one thing, but then charges for amenities or common areas creep up. How do you guys verify the *real* monthly outgoing, including things like common area electricity or specific amenity usage charges, before finalising? Don't want any surprises. Proximity to a good hospital is also key. Any tips on checking these hidden costs?