Touring bikes tend to command a premium and it may be difficult to find one in your price range. Plus once you buy a used bike, it generally takes some money to get it working right since the consumables need to be replaced. A more cost effective option is to find a vintage mtb. They tend to go for a lot less than a road bike and they are easy to mod to make them good commuters. On a longish commute, drop bars are a plus though. You can fairly easily and inexpensively add trekking bars to a mtb which will give you more comfortable hand positions for a long ride than the stock flat bars.