Is this serious fixer-upper worth it?
I looked up the property (I think I found the right one).


Because this was built 1900s-ish, assume you need to replace all plumbing and electrical. Assume all paint is lead paint. Assume there's asbestos somewhere. Assume you'll need to strip all walls to the studs.
Thankfully, the water damage does not appear to be flooding-related, but from rain.
The water damage appears to be highly localized in specific areas, but bad enough that there's holes in the floor at those points.
The roof appears flat, or generally unsuitable for the climate. This is going to be an ongoing problem for the building.
There's unlikely to be any insulation. (This is actually a good thing for a building with this much damage, as it means the structure can dry out properly, but you will need to fix that.)
The listing talks about the certificate of occupancy. Basically, until the building is fixed, you don't get to live in it. This will generally require you to finish your work, not just fix the roof and make a couple rooms livable. Talk to someone about what that means in that particular city.
The structure at the back appears to be sagging a bit. Not sure if it's a trick of the camera or not, but I don't trust it.


My non-expert opinion: the basic structure appears to be sound. However, you won't be able to move in until most of the work is done. (RV in back yard might work, depending on city rules.)  For a structure this old, there are serious health issues associated with some renovations that a professional would be better suited to handling. This is definitely hard mode for a DIY project. Restoring this is basically a full time job over months.