The code violation list will have CODEs on it. you need to get the key for the codes.
Some properties just have tall grass that needs to be mowed. Others have a fence that needs to be fixed. These are not the properties you need to do marketing to.
You are looking for the properties which the city has said no one can live in it until it is repaired. Some cities call these RED TAGS because there will be a big red tag on the front door. These are the properties you can get for 90% below market then wholesale for a big profit. They can all be fixed up.
The city will have a list of what repairs need to be done to the property for it to get a certificate of occupancy again.
To reach the owners of these houses, you can look up the address in the country tax records or you can talk to the neighbors on either side to see if they have a phone number for the owner.
Another way to get their attention is to put a We Buy Houses sign in the yard. You will likely get a phone call.