So people don’t upgrade until the redemption periods have expired.

They’ve been on month to month lease since their lease expired last year.

With the backlog the city is generally not rejecting deeds due to shortages, expired lien certs or even for old checks.

If they also have a longer term lease (anything that is not expiring in probably 60 days), then you really have no unit to move into. 

If I ever want to pull equity out at a later date this is a good selling point. 

Either partner up with someone that will get the mortgage and you'll provide the capital or buy a building for cash and then refinance and pull your cash out at a later date.

Or how would you use the tool to calculate the ROI as it has not been rented out since the initial purchase date?

Works great.I wouldn't bring up that I have an agent on the first letter or first date if possible. 

It's been my experience that, buying such list of any real estate property prospects, that I always find the list to be out-dated and inaccurate data.

You will have access to the mls but also to Imapp (great free software to search public records, and create mailing lists such as deliquent property taxes, expired listings, absentee owners, ect).