Hi Sam Williams, congrats on taking action and getting started. From my own experience, I feel like there's a lot of value in starting out with tax delinquent data that one's obtained direct from a county, before jumping into the list providers, so you can work out questions like this (okay I have a list, now what), and make sure that land flipping is actually something you want to stick with, before you sign up for a service with a recurring monthly bill. Do you have any specific questions about the structure of the particular county data you're looking at or what to do with it? Assuming it's in some kind of spreadsheet type format, maybe if you posted some sample fields that have you stumped we could provide some more specific input.
Absent that, I think I would just say that at the most fundamental level, you need enough data on each property to determine:What is it? I.e. is it Vacant land or Improved property (has a house, commercial building or some other improvement, such as an oil/gas well, on it) - if you're only trying to buy vacant land right now, this piece of data is obviously important in order to filter your list down to only vacant parcels, so you don't send mail to a bunch of people that are behind on their taxes but have houses on their property. Other factors you'll want at some point include the property address or county's description of the property (often vacant land does not have an address assigned), and the size/acreage of it.Who owns it and who & where would you send your mail to?
Hopefully the county list includes the assessment information about each property, including the county's assessed value of the land, all improvements, usually some type of other/extra factors, and the grand total of the current property assessment. This data is very helpful when filtering out the improved properties as referenced in the first bullet, above, and for filtering out properties that are not in a price range you're currently interested in. For example, if you know you won't be able to do anything with a $1,000,000 property, or if $500 properties won't work for your model because you're going to close through a title company so the transaction costs will be more than the property will likely resell for, then you might choose to cut these properties from your list before sending mail.