I lent a friend the down payment for her house, and now she refuses to repay me. There are court documents that prove I lent her the money. Can I put a lien on the house to recoup the down payment?

Why not just take her to court for the amount? Putting a lien on it will not get you your money back until she decides to sell the house.

A lien is an encumbrance on an asset preventing its sale until the debt is established. So that doesn't help you recoup the loan immediately. Also you can't place a lien unless you have a note that lists the property as collateral or a judgment against the debtor.

What court documents prove the loan?

... Also you can't place a lien unless you have a note that lists the property as collateral or a judgment against the debtor....

A note, all by itself, is not enough to file a lien.

A note, all by itself, is not enough to file a lien.

Depends on the note. My bank has a lien on my house because I signed a mortgage note. If the note lists the property as collateral I'm pretty sure it can be used to record a lien.

Look up the limit for Small Claims on your state.gov website. They vary a lot, often between 5K and 10K. How much did you lend? Is interest being charged?

Depends on the note. My bank has a lien on my house because I signed a mortgage note. If the note lists the property as collateral I'm pretty sure it can be used to record a lien.

Your bank has a lien because you signed a mortgage, as well as the mortgage note. The mortgage is the lien, the note is not.