flats going away even more quickly

All flats that I'm interested in are gone within 3 days after I viewed them. Or before I view them. Except one that no one takes. So I'm trying my luck on this rather insecure flat - everyone can freely walk to the front door, and that's the only door you have to break to get in... even worse than public housing estates in Hong Kong which have 鐵閘. And in a place with this crime rate...