Your lien rights come with the work
If you improved the property, whether you added a roof, a system or a wall, most states give you the right to file a mechanic's lien on it. That's true whether you contracted with the owner directly or worked under a GC. A lien is filed with the county, attaches to the property title, and has to be dealt with before the owner can sell or refinance cleanly.
Lien rules change by state, by type of property (residential, homestead, commercial) and by who you contracted with. Deadlines are strict. That's the part we handle.