However, the original title company said even though the transfer occurred during the original owner "MARY" did not own the property, the liens associated with JOHN could "stick" onto the property.

The cost associated with doing so depends primarily on the current height of the basement, and whether or not you have to underpin.

Also, any ancillary costs associated with researching the title and making sure there are no additional hidden liens you may be responsible for?

You should also contact the local Association of Realtors office, if they are members of it, and file a complaint there as well.

Join a local Apartment Owners Association.  

What are the costs associated with filing paperwork to bar the right of sale?

Anecdotally, this has been very surprising to some people who previously associated Natick with the mall & not much else. 

This option is nice because you have a smaller group of people, less upfront costs associated with legal as well as fewer additional costs through the life of the hold.

I'm a local investor and have just recently started connecting with other local investors through the Rockford Apartment Association (RAA) and I'm looking forward to meeting many new people tonight at the meetup. 

If you want to acquire the property associated with the certificate there will likely be administrative costs associated with the tax deed application and in at least one state with which I am familiar (Florida) it is possible that significant other costs could be incurred but that process is only important if you elect to invest there.Another pitfall in tax lien investing is that in most, if not all states the certificate expires after a specified duration.