A lien is a form of security interest granted over an item of property to secure the payment of a debt - even hospital bills. Any real property that carries a lien can be forced into sale by the debt holder, in order to collect what is owed, but I think the threat they will force your home into sale for $4000 is not rational.
Notices are usually required and formalities must be followed.
Don't let the collection company bully you.
Read my Legal Guide..... COLLECTIONS
These things are illegal.....
Calling repeatedly or continuously. The federal debt collection law, the FDCPA, states the legislative intent that repeat calls are harassment. [15 USC 1692d] § 806(5) (So, too, the Illinois version)
Threatening action they cannot or will not take. Such threats might be to sue or file charges against you, garnish wages, take property, cause job loss, or ruin your credit when the company cannot or does not intend to take the action. [15 USC 1692e] § 807(5)
Inform a third party about your alleged debt, unless you have expressly given permission. This does not include your lawyer, the creditor, and the creditor's lawyer, a credit reporting agency, your husband or wife. If you're a minor, your parent. [15 USC 1692c] § 805(b)
Asking you to pay more than you owe is also illegal. Doing so using obscene, abusive or profane language during a call is considered harassment. [15 USC 1692d] § 806(2)
Calling before 8:00 am or after 9:00 pm. Debt collection telephone calls during these times are considered harassment. [15 USC 1692c] § 805(a)(1)
Calling at times the company knew or should know is inconvenient. This is aslo considered harassment. [15 USC 1692c] § 805(a)(1)
Using or threatening to use violence if you fail to pay off the debt. [15 USC 1692d] § 806(1)
Repeatedly calling a third party to get your location information, which they can only do once unless the company has reason to believe the information previously provided is false. [15 USC 1692b] § 804(1).
Misrepresenting the amount you owe. [15 USC 1692e] § 807(2)(a)
Asking you to pay interest, fees, or expenses not allowed by law and that were not stated or included in your original credit and/or loan agreement. [15 USC 1692f] § 808(1)