When we looked at the database together, the inventory for my area is low and there is really not any units out there right now that are identical to mine. 

@Joe Gore - Here are the databases for the criminal check.

His tracking data base is awesome....and used to be free.

It uses the same database as Realcomp which is the official MLS that local agents use.

Out of area PR's should be priority targets.Most people add about 25 cases to their database each court visit.

I'm at the point where I can collate the information and send out mailers to the people on the list, but this leaves me with a few questions: How should I update my database when I get new lists every week or two?

I've considered doing something similar but using tax records database to do a quick search of owner addresses in states different than the property.  

Lastly, they have a large database of contracts, agreements, documents, etc. you might need as a real estate investor.

it depends on the jurisdiction. i would start by looking for your county's GIS services website and see if they have a property records database you can pull. there will usually be some sort of indicator for primary residence or homestead tax deduction, or worst case you can see if the mailing address matches the property address. otherwise try list source and pay for a list.

Using online data bases (such as Zillow, Trulia and Redfin) come across as unreliable or inconsistent in terms of evaluating comps.