To answer your question regarding timing, this will depend upon the deal made between the HOA and previous owner. The settlement could have been for a payment made over several months or may be due in full by a certain time period (typically 30 days). You can try to call the HOA representative to get an answer or details regarding the settlement, but they often will not release this information to third parties.
Something is not right here.. who is selling the condo? the HOA or old owner? If the old owner wants to sell it the owner can sell it immediately subject to the lien and pay the lien from the proceeds. If the HOA is selling it the old owner should not be involved -- they have already foreclosed and own the unit.
Now if you put the offer into the HOA and the HOA owned it subject to some right of reversion to the old owner.. then all should be well also. Now that the Lien is "settled" the amount is liquidated, i.e. a sum certain. Therefore, you could buy it now and the HOA and the owner split the proceeds according to that understanding.
I would advise making an offer giving the owner a 2-3 day right to accept the offer and closing cash within a 30 day window. If they do not accept they may be waiting for other offers ... and your patience is working against you.
Answering this question with general knowlege of the law does not create an attorney client relationship and attorney cannot be held responsible for how the questioner uses this information.