@Mission Flegg
Interesting post as I am literally working on this exact issue right now.
There is a tax sale in progress in my area. Like elsewhere, the county posts the list of upcoming items for sale 8 weeks or so before the sale starts. People either contact the delinquent owners before the items go to sale or ultimately wait for the sale and bid.
I am trying to get ahead of this process. The county sells a list of all delinquent properties, meaning any properties even one payment past due. I'll merge this list with owner contact info (gotten from other sites) and build a contact list. I can then target owners > 3 years past due, giving me a couple years before they go to sale to market to them.
I have experimented with putting similar data (all tax sale properties) in google earth so I can quickly view by region, with color coded pins to represent the amount of improvement on lots, etc. It is super handy for quickly viewing areas with delinquent items. I have to manually check against property radar for initial validation, but hopefully will automate this more. I have another post on BP with sample data.
I think once I have the actual data from county I can track trends for areas are well and do some deeper analysis, or marry the data with other GIS data (incomes, rent/own, etc) to build a better model.
I'd just contact the prop tax office for the county and ask to speak to someone in data services, and that you'd like to purchase tax data for current and/or delinquent owners. It worked for me.
Regarding your other question, in the counties I've looked at the parcel information includes info on whether the property is improved or not.