County records should contain any liens against the property. That's not to say nothing has been misfiled, or in the process of being filed when you do your search.
You need to find out your local laws (usually state) on the ordering of liens and judgments. And you need to know when lien is being foreclosed. In a simple case of a first mortgage and a HELOC, and for CO law, its like this. If the first is foreclosing, and you buy it, then the HELOC lienholder has a redemption period when they can "redeem" the property. They would pay you off, and take possession, should they choose to exercise their right. If not, their lien is wiped out. If the HELOC is foreclosing, and you won the auction, the first would still be in place, and you would become responsible for it. The basic rule is that they are ordered by time. First in time, first in line. However, there are a few exceptions like some tax liens, and HOA fees up to a certain amount.