What is the chance of being sued for a outstanding credit card balance under 700 that he credit card company has already charged off?

Who would sue you? If it is charged off the CC's have given up because it is not worth their time or money. but it could be sold to some collection crooks that will tell you that they will come after you. If it was wrote off they can't legally collect it, but they are known to LIE and if you make any kind of payment you could again start the whole thing over. Chances are the statues of limitation have run out and then it is noncollectable by any one unless you pay on it.