Water filters normally consist of a sediment pre-filter and a carbon pre-filter.  If you have two housings, two filters, and a faucet -- and the filters are in good condition -- all you need is a Reverse Osmosis membrane and housing, a tank, a carbon post-filter, an automatic shutoff valve, a drain saddle clamp, a capillary restrictor tube, a bracket, some fittings, and a few feet of 1/4" tubing. We can send this all to you for just $290 (plus $10 shipping).