I built a house for my at the time common-law spouse, I incured costs of 40 plus k not to mention labor. She has been leading me on saying 'I am going to pay you' etc. It has been almost three years I have yet to see a dime and now I would like to place a lien against the property. Is it too late?

Was there any agreement that she would repay you? Were you living in the house at that time and now?

The problem here is you may have a hard time proving this was not a gift or not for your own benefit as well. If you think you can, then file suit and, if you win the suit, you can place the lien.

Our relationship dissolved before completion of the house. I completed the construction on promises that I would be paid. I have not lived in the house at all.
So I would have to sue and win before being able to place a lien?

You can try filing a mechanics lien, but you will have to back that up by going to court to affirm that there were agreements to pay you.

You should review the mechan's lien statute (As I recall, in Canada they call it "construction lien", or something like that, which actually makes better sense.), to determine whether you can file one. The requirements vary, including how much time has elapsed from the time the work was done, and whether the property owner has signed a consent to lien.