Since California is a community property state, If you're getting an FHA loan or a VA loan they have to run your dad's credit report. If you're getting a conventional loan, they do not have to run his credit, however the lien will come up when the title company runs their search. It would be a good idea for your dad to make payment arrangements now.
Elva A. Wormley
Office (408) 615-8500
C2 Financial Corporation
2845 Moorpark Avenue, Suite 209
San Jose, CA 95128
NMLS #331981 / CA BRE #01274093