$700 for a 1986 Honda XR600R; already had a title and DOT knobs. Threw on new chain and sprockets, homemade tail bag, a brake light switch from my pile of goodies at home and a mirror/GPS mount. Have less than $1000 in it and still tight as new.
Sub-$2500 bikes are easy to come by. Having mechanical skills and knowledge is incredibly helpful. Now-a-days, with so much ethanol problems, if you can work on a pair of carbs, you can find cheap bikes allllll day.