Plugin request – Force backlink

Hello,

i need someone to write WordPress plugin. You can use it as Your plugin (im sure it will be used, did not found anything like that yet) or i will buy it 100%. But i need as low price as possible, like $50. You can use plugin on your own, i will just contribute for example.

MAIN DESCRIPTION:
WP Plugin For public WordPress article directories and blogs where people can register as Author and publish their articles. Author must link to the blog to be able to post new articles.

FROM Author POINT OF VIEW:
On New Post page he can see

a) Field with URL where will be filled his reciprocal url to our blog
b) or Text telling him he need to enter his URL with hyperlink to Plugin config. page.

PLUGIN CONFIG PAGE:
There are HTML and BB code of 5 random articles from the blog generated by plugin. and he choose one link and he will add code to his webpage. (only reciprocal websites not existing in blacklist – admin user can modiffy blacklist in plugin config page). Then he will enter his backlink url at the config. page. On submit, backlink URL is veriffied for existence, if not found, he need to enter correct one before he can post new articles. From now on, this url will be prefilled on every New post page and after every post submitted. The backlink existence is checked (is it server load friendly? or we need to create cron?), If not found, backlink field is cleared and he enter his reciprocal url again in plugin config and he canot post new articles untill entered ok and veriffied on plugin config page.

If backlink check on every post is sent is too intensive task (can be run at background like XML Sitemap plugin sitemap generation), cronjob will be used. Only Admin User can see Cronjob URL with hash.