You can call before you have every document. The property address is enough to start a conversation. If handy, bring a recent tax bill or delinquency notice, a mortgage or creditor payoff statement, a court or judgment notice, the parcel number, and any deed or recorded document related to the claim.
The tax collector or office named on a tax bill or notice can confirm the current tax balance and any stated status or deadline. A lender or other creditor provides its current payoff. The title company checks ownership and recorded claims for the sale; the County Clerk's land records can help identify recorded deeds, mortgages, and other documents. Assessed value is a separate figure, not a lien payoff or sale price.
Start with what you have and tell us what is missing. You do not have to resolve the balance or collect every record before calling 888-274-5006.