I would get a Realtor to work with, and they can do some research on the property or properties you are interested in.
If it is not on the market, there's still likely an option to make an inquiry to the owner. But, if the building is structurally deficient, you'll likely be looking at a whole can of worms to deal with to purchase and ultimately do something with the property.
The red "X" is for vacant properties. If there is a fire, first responders will not risk life and limb to search for occupants. If you are looking to buy properties, contact me.
I have seen quite a few of these buildings for sale.
If you need more information about specific properties, feel free to reach out to me and I'd be happy to see if I can assist you further.