Take your time and look on Craig's List as said earlier. Some great deals out there to be found.....
Things I will look at for mine when I get to that piece of equipment:
How much am i going to use it and what for. Go a little bigger then you think you will need, leaves room to grow.
Weight and size..... is it staying in one spot or are you going to have to move it around?
If only doing a little (less then 20lb at a time) I do not feel an automatic slicing feature is needed. IMO just something else to break. For me it is the less moving parts the better.....
How easy is it to breakdown for cleaning? If you can, actually take it apart and see how hard it is to get everything clean.
How hard is it to find replacement parts (blades, gears, motor, etc.)? If the machine is old you will have issues finding these parts and sometimes actually pay more for what you are able to find.
Either a sharpening attachment, as mentioned earlier, or a place you trust that can sharpen the blade. Depending on what you cut, your blades will get dull or burred quickly. Then you get some ugly ends on your pieces as you cut.
Price vs. Time Frame........ If you have time you will find what you are looking for close to your price range, if you need it now you will pay more for it....
jeramy