It is often the case that tax deed sales to not properly extinguish claim to the property. Accordingly, many claims and liens remain. In addition, association obligations pass to the new owner, so even when someone acquires a unit via a tax deed sale, the prior owners' obligations come with it.
This is a very dangerous area to get involved in without specific legal advice relating to the particular property or unit.
Please note that the above is not intended as legal advice, it is for educational purposes only. No attorney-client relationship is created or is intended to be created hereby. You should contact a local attorney to discuss and to obtain legal advice.