Hiya myermay
Property prices have come down quite a bit over the last 18mths, but are now recovering. Mortgages in Sydney are notoriously expensive. I am a upper northern beaches resident, being in Belrose and I work in Chatswood. If we had the cash we would be nearer to Manly. If I were you I would rent for a while to get the feel for the area.
You don't say if you want a house or a townhouse or an apartment - that will make a big difference to what you can afford. Have you been checking out realestate.com.au? I see a 3 bedroom house in Beacon Hill that looks to be in your price range - but probably only because it is on a pretty busy road Property No. 104050962 . This would be an area worth considering but you would definitely need a car.
If you wanted to be a bit closer to the city and live in an apartment then I found a nice looking place in Lilyfield Property No. 103853776 $529,000 Bedrooms3 Bathrooms2 Car Spaces1
Three bedroom, two bathroom apartment located opposite Callan Park and minutes to the CBD and Leichhardt's bustling Norton Street.
Open plan lounge and dining area, large private sunny rooftop terrace, security parking, separate study area and internal laundry.
Located within a small well maintained block with easy access to the vibrant city lifestyle.
HTH