It's not possible to know based on the information you've given us. You will need to have the seller tell you the manufacturing date (NTSC-U) or date code (PAL), which should be located on a small sticker on the bottom of the unit (note that it's tiny). If it's been manufactured before April 2011 (date code 0C, 0D or 1A) then it's CFW capable. Unfortunately there is no way of knowing the date in the case of NTSC-J consoles.
There is a very slight chance that a console that's supposed to be CFW capable won't be, specifically in the case where broke and officially serviced by Sony, because they sometimes just replace the entire motherboard, but that's extremely rare. If you want to be 100% certain you can ask the seller to verify it with MinVerChk or bgtoolset.