Nothing in this chapter may be deemed to fix a greater liability upon an owner in favor of any claimant under an original contractor than the amount for which the owner would be liable to the original contractor; provided, however, that the risk of all payments made to the original contractor is upon the owner after the receipt of notice that a lien is claimed by a person other than the original contractor; and provided further, that an owner does not have the right to offset obligations of the original contractor unless such obligations arise out of the original contract.