A lien waiver is very common today and protects you and your bank. I am building a house now and any contractor who does manual labor on my house signs a lien waiver immediately after I hand him a check. For material items all you need is your receipt. Example, electrician wires an outlet, because of the labor involved he signs a lien waiver. The guy delivering the gravel for my driveway does not sign one, I got a receipt showing I paid for the rock.

Anybody who works on your property and feels like they were cheated or slighted can file a lien against that property for the amount of the dispute. In Iowa they have 90 days to do so. If they sign a lien waiver they are essentially waiving the right to file a lien. You can not transfer or sell the property until that lien is settled.

Otherwise the banks would make you wait the 90 days before giving you a mortgage on a newly constructed house. They don't want any liens on it.

Removing liens is a hassle but it is done frequently after the misunderstanding with the contractor is settled.

Call your mortgage banker or lawyer for a copy of a lien waiver and use them.