Depends on how big of a budget you want to spend. If you plan on staying in nice motel rooms, average about $70 a day. If you stay at the mom and pop hotels, they are considerably cheaper at about $30-40 a day.
Or, you can plan your route along the KOA campgrounds and stay VERY cheap.
You also need to take into consideration the route you are going to take. Where are you going? How long do you plan on being away? Food can get pretty pricey if you hate eating fast food like most of us do.
Body just can't handle all the calories like it use to!
I purchased a book called road trips USA from RIDERwearhouse phone #1-800-222-1994, or www.aerostich.com. the book lists a lot of points of interest along many of America's 2 lane highways. It also lists places to stay and eat that are generally reasonable because they are not on the interstates. The Aerostich catalog also has a great amount of useable stuff for the motorcycle traveler. I have purchased many items from them and are very happy with the products and service.