When a parent dies and the estate has not posted notice to creditors can a child enter into legal agreements?

When a parent dies the estate must be probated in order for title to real property to pass to the heirs legally and for the court to appoint an Executor or Administrator. Only the court appointed fiduciary will have the authority to access accounts. Until the estate is probated there is no one authorized to enter legal agreements concerning the property. You should consult with an attorney who specializes in probate.