Just replace the cushions and the cloth by a good mechanic and the table will play great. Research here to find reviews/recommendations for cloth and cushions to use. I just put on Artimis cushions and Simonis 860 on an antique 9' Brunswick and it just perfect, probably top dollar on both though.
As for other things to check for, post pics and description in the 'Ask a mechanic' section. Also mention what room it will be located in and who will use it. Will children or teenagers be using it? Casual or serious player(s)? That way, you can get the most appropriate advice.
Generally, as long as the table has good bones, and the price is right, you are good to go, as long as you're willing to have a professional mechanic set it up and be willing to replace cushions/cloth as needed. The table may very well be your smallest cost.
The table must be slate (I prefer at least an 1 inch), but for general home use, 3/4 is OK. I wouldn't use 1/2 for anything. The frame must be solid, preferable real wood (no pressboard or anything that can peel).
Also check the pockets. If they are drop pockets, are they usable in the condition? If not, a new set can run you around $250. If it's a gully (ball return), be careful and make sure it functions properly. That's a risk you are going to run if the table is not together.
If in pieces, do not buy if table or frame is stored or it's side or if the room conditions are horrible (wet, mostly).
Be very, very careful if purchasing a table in pieces. Make absolutely sure all table pieces and hardware are there. Or, at least, determine what is missing and what the replacement cost will be. I spent over $200 on replacement hardware from my antique Brunswick table because they were missing. I knew this up front though.
good luck
