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A month is more than sufficient for the one-way trip you describe, you could even make it in three weeks and have a week to get back to Boston by a more direct route if you should need to. For a solo trip of this nature, a ballpark figure on cost would be about $3500-4000, assuming you use your own car. Renting a car would cost an additional $1000 or so, plus a several hundred dollar drop-off fee if you're only going one way. Adding additional people does not increase costs that much. If you all share the same motel room, then your only added cost is food and the per person cost drop accordingly.

Since you are most interested in cities, you should be looking at Cleveland Chicago, St. Louis, Memphis, Austin, San Antonio, El Paso, Phoenix, and Los Angeles. But don't overlook the scenic aspects of the Great Lake such as Indiana Dunes National Lakeshore, the many wildlife refuges along the Mississippi, or some of the natural wonders of the Southwest such as White Sands National Monument, Carlsbad or Kartchner Caverns, Saguaro National Park, Joshua Tree National park, and the Pacific Coast Highway.

AZBuck