Generally, the Statute of Limitations is 3yrs, but there are nuances to that rule. Harassment is NEVER okay, and under the FDCPA, you are entitled to $. You really may have a great case against CCR. Please feel free to contact for a free consultation.
Evidence of debt (contract) and Sufficiency of proof (by affidavit) are legitimate issues - also look at the statute of limitations. Sometimes, they've violated other collection laws by harassing debtors etc. There are a lot of ways to litigate against debt purchasers.
You do have a great issue for litigation in Maryland. The bottom line is your answer rests in the types of affidavits and attachments relied upon, in addition to other documents that often accompany a debt buyer's purchase. Sorry, no solid answer for you, but you really do have a case where you need to consulte with an attorney.
Yes, you NEED to start thinking DEFENSE. Try to short sale the house - and hope that the lender either agrees to forgive the overrage or does not pursue it. If the attempt to pursue this debt, look into bankruptcy to protect your retirement funds and what assets you can shield in bankruptcy.
If you were never served, check the records to see if they were there was "service by posting or publication". If not, check the court file for the affidavit of service.
Use that false affidavit to vacate the judgment - sue the process server for damages.
What was the date of medical treatment?
Judgment liens are only effective against real property in the county where judgment has been entered. The only way to place a lien on property out-of-county is to enroll it by filing it with that county court's clerk. The first issues is whether or not you have a valid lien on property.
The second issue, would be that an administrator of the estate should have cleared all debts prior to distribution of assets... when a property is transferred, an abstract automatically runs a lien AND...
No, they cannot refuse to pay it. If you relied on their statements to your detriment, it is their responsibility. To take it a step further, you can even sue the complex itself for hiring workers who were negligent in their duty (the lease agent owes you a duty of care to either PROPERLY inform you of move-in information... or not offer it at all).
In reality, this would all be overkill for a few hundred bucks - which may not be worth your time. But if you want to pursue this, this is...