I built a crf50 with a takegawa 88 kit, tall bars, and stiff springs for $500. You have to be patient and find good deals here, on ebay, and on craigslist.
somebody on here is selling fixed up complete 70 forks for $150..and put a 70 swinger on it ...add a $100 shock....used Fox Float or Ishock...and you are in there. much under budget and a decent ride...you would even have cash left over for a pipe n filter/jetting combo....I have a Kitaco replacement shock with a heavier spring that I will sell