tax lien cert. balto condo good/bad?

I have purchased a few tax lien cert. in balto with no problems. Now have an eye on some cert. that are “condo” but have noticed no one “in the know” buy condo certs. Can anyone cast a little light on why, is there a pitfall, low resale or is it related to problems with the condo assoc. Everyone knows when you have a condo you get a new family along with it. I can’t see it being values because some condos in Baltimore are on par with home sales. I did have one thought that the condo association will/must/can step in and pay the past due on behalf of the owner to maintain control, and we know how they like to “control”, could that be it? Any info appreciated.