I am Prime Contractor performing mitigation/restoration commercial work. Contracts are more than $25,000. What is required and when required to be filed to protect lien rights.
The number of importance is $75,000. If you exceed that you will need a different license. You need to also be careful to either have a mold remediation license or to avoid doing that work.
Liens should be filed after work is completed if you are unpaid. However, a well drafted contract is the first step.