I have been living with and caring for my ailing parents 24/7 for some time, without getting paid. I was unable to work because I took care of them full time. About 6 months ago we entered into a caregiver contract, stating that they would pay me every month.They didn't pay me. They both passed recently. Moms house was left to me and my 3 siblings. Can I place a lien on the property in order to recover the money that they owe me?

... Can I place a lien on the property in order to recover the money that they owe me?

No. Your siblings don't owe you, but perhaps your parents' estate does. What you want to do is make a claim against the probate estate. Has a probate petition been filed with the court? If not, someone (probably not you because of a conflict of interest) needs to do so.

Do your siblings disagree that you are owed money?

My siblings want to sell the house and have it split 4 ways. Or one of my siblings talked about buying the other 3 out. My siblings don't care if Im owed money or not. They just don't want to part with it. I have been living in this house, caring for my parents for the past 4 yrs, and would like to buy the house... but since I have been unable to work for the past 4 yrs, Im not in a position to do so.

Sadly if you wanted to be able to buy the house, your parents before they did, should have helped in the will make some arrangement for that.

At this point, depending on how the deed is written, most likely it will go to probate court and they will decide how it will be sold. You can as noted make a claim against the esttae for the value of your contract.

They may of course argue or try to fight the contract on several factors.
one of which is that if they made NO payment at all toward the agreement, that without some form of payment it was not a valid contract, no payment or consideration was done from their point. So I guess why did they not make some form of payment and why you did not sue them sooner for non payment of the contract.
** sorry fighting in probate between family can get very nasty at times, so if they don't want you to get that extra money, they can fight it.

... that without some form of payment it was not a valid contract, no payment or consideration was done from their point. ...

It's elementary contract law that the consideration is the promise. In this case, the promise to pay you for the service. Assuming the contract is clear on that point, that shouldn't be a problem.

The problem right now is that evidently you either haven't gone to probate or the deed is somehow crafted to avoid probate. In either case, you can force a sale. But, if probate can been avoided, your claim against the estate for your services might be avoided as well.