Purchases of real estate as provided by law may be made by a state department on written contracts providing for payment over a period of years but the obligations thereon shall not constitute a debt or charge against the state of Iowa nor against the funds of the department for which said purchases are made. Purchase payments shall be made from only capital funds appropriated for that purpose. All state-appropriated capital funds used for any one purchase contract shall be taken entirely from a single capital appropriation and shall be set aside for that purpose. In event of default, the only remedy of the seller shall be against the property itself in rem, pursuant to chapter 654. In no event shall a deficiency judgment be entered or enforced against the state or the department making the purchase. The provisions of chapter 656 prescribing how a real estate contract may be forfeited shall, in no event, be applicable. In a foreclosure proceeding pursuant to this section and chapter 654, the department making the purchase and the attorney general shall be the only defendants who need be named and such department and the attorney general may be served personally or by restricted certified mail. The department and the attorney general shall have thirty days from the date of completed service in which to appear.