File a lien? Even if the house is worth a jillion dollars, you can't file a lien.
Liens can be filed by so-called "mechanics" (workmen, materials suppliers, or equipment suppliers) doing a work of improvement to real estate. Liens can also be filed by tax collectors like the county and the IRS. Liens can be filed (recorded) by the consent of the parties, as when the owner takes out a loan. If you sued the friend, won, and got a judgment, you could create a lien by recording an abstract of your judgment.
It is also possible to tie up property before getting a judgment by filing suit and promptly moving the court for a writ of attachment. This is a complicated processand not advisable where the property is under water due to its market value being less than prior liens.
An ordinary person merely claiming to be a creditor cannot "file" or "record" anything to create a self-help lien.
As the previous answer indicates, liens are honored in seniority order, based upon when the lien was recorded. All claims recorded prior to yours would be paid in full from proceeds of anyone's foreclosure. In your position, your lien, if you could get one, would probably be so low in the pecking order that there's be no money left when your number came up.
