I came across an abandonded C3 system with no structures, only two cold POSes that seem to be left there years ago.
Now that ratting in null has been nerfed, WH ratting is relatively more attractive than it used to be. As a rough estimate, you should be able to get at least 200m/h of ISK ratting in a faction battleship with good skills.
Also, the system has 3x Lava, 3x Barren and 4x Gas Giant planets, which means good PI opportunities, although PI prices have gone down recently. However, the POCOs obviously are not included in the price.
Asking price is 1b.