I had look into HOA and tax lien sales in the past, I am sure each state little different, here in Indiana, such lien doesn't actually give the title right but only a convey to the title, meaning its not a true title but only temperately ownership of fraction of the title.
HOA and tax liens are priority liens ahead of mortgage liens, 99% of time bank will not let it happen, but there always mistakes can be made..
after investor bought the HOA and tax lien, to truly own the property, investor need to foreclose the mortgage lien but in this case, this company is very smart, they not looking into owning the property but only trading small amount of investment for temperately ownership for short period of time.
another risk is, if the owner still living in there, very difficult to force an eviction, because in court's eye, they still the owner. the best chance is the property already a rental property or vacant, I would think cash for key is the fast and best way.