How long does a lien last? I mean does it last forever until you either get rid of property or sell it? Is there a way I can look up my propert online or do I have to go to courthouse?

Some counties have online records, most in the US does not, and online is often not up to date in areas they have it. So it is always best to go in person to the courthouse and check if there are liens.

To get a lien ( besides a mortgage or lien you sign for) they will have to have gotten a judgement first in court.

Also yes, liens last forever or until paid. And you have to sell the property for enough to pay it off to be able to sell it.

Real estate liens last until the property is sold. When the lien is satisfied the property can be transferred to the new owner otherwise no transfer. Go in person and check it out yourself at the courthouse.