Hello, I hope you find this helpful.  ebay features many great bargains on electric shavers but I will stick to my favorite the Braun Syncro.  Any used shaver you buy will need a replacement cutter block ( blade ) and the Syncro series replacement cutter is priced from $23 to $29 including the foil screen.  The used Syncro series Shaver should cost $40 to $70 depending on model. There are the 6000, 7000, &  8000 models. 

The Syncro Shaver works best with the base the Clean and Charge unit which is priced at about $20 used or new.  Also a crucial part in the Clean and Charge process are the Clean and Charge liguid solution cartridges that last a month with normal use.  They should cost $5 a piece.  The liquid cartridge is inserted in the Clean and Charge base, cleaning the Syncro Shaver.  Braun Syncro Shavers are NOT wet shavers.  They are Dry only. 

The best way to clean a used shaver is first using a small painting brush.  Thouroughly getting in every crevice.   The longer the bristles the better.  And then cleaning with baby wipes.  They have just enough alcohol to clean, dissinfect, and refresh without over wetting the shaver and it's parts. 

Always ask the seller about the electric cord.