Legal Question in Real Estate Law in California

No, but some contracts must be notarized, most common being contracts for sale of land, but there are others.

Only a few kinds of documents must be witnessed.......the most common one coming to mind is a will....but even there an exception exists for so-called "holographic" wills which are entirely in the handwriting of the testator, dated and signed. I cannot think of any kind of contract that requires witnesses, but I suppose a party to a contract could make witnesses a condition of his/her/its participation in the contract.