Promissory note and first lien

[Pepe Catala]

I hold a promissory note on a small RE development company managed by a friend. The note is ungaranteed and as far as I understand it's junior debt that could get unpaid fairly easily. Is it a standard practice to secure the note being the first lien on a mortgage? The money is not tied to specific projects, so how would that work? (they manage multiple projects concurrently but the co does not hold RE long term)

I am guessing this would bring down the interest rate.  Asking as I was thinking of lending them more, but need a way to secure the investment. Open to other ideas/practices.