Ned, thanks for jumping in here. I've been busy trying to crack this nut and I have made some progress. First of all, I should have just moved on to another county but I wanted to start with a particular county and I couldn't get it out of my head. As you suggested, I looked up the law and in Indiana they have what's called the Access to Public Records Act (APRA). In that law they have a form letter for use in requesting information. The agency has 7 days to respond. If they can not provide the information, they must state the statute that prevents them from releasing the information, etc. I sent the letter attached to a polite email to the clerk who refused me the first time. The response came from the County Treasurer who said that the records are available in their offices from 8 to 5 blah, blah, blah. In other words, yes they have to let me have access to the records, but no, they won't make it at all convenient (even though they can).
The tax sale data is out on each county's website here in Indiana - until the sale is over. Then the list is GONE. It is a very brief list. It has the owner's name but not address. That is why it doesn't really satisfy what I really need in a list.
I have tried signing up for both Rebogateway and AgentPro247. I got full membership in both because I can't tell what the data looks like on a trial with either of them. For tax delinquent lists AgentPro247 is the way to go. I can not speak for the quality of the data - yet.
My mailing list is all set up and I am going to order postcards as soon as I get done with this post.