I am a snow removal sub contractor. I recently received a lein waver to sign for payment of my services. I have not been paid yet and the General contractor wants to have me sign a lein waver before he pays me. Is this legal? Sounds like I should get payment first before signing away my rights. I am located in Minnesota. What are your thoughts?
First, I'd note that mechanics lien rights are generally for those who have permanently improved the project property. And, when the work doesn't permanently change the underlying property, as with snow removal, lien rights might not be available in the first place.
With that being said, you're correct that unconditional lien waivers are designed to act like receipts after payment has been made. Though, if a conditional waiver were exchanged prior to payment, that could certainly be appropriate. More on the difference here: Unconditional Lien Waivers vs Conditional Lien Waivers.
With all that in mind, note that Minnesota generally prohibits the waiver of lien rights or bond claim rights prior to receiving payment, as Levelset discusses here: Minnesota Lien Waivers Guide and FAQs.