Whmcs, boxbilling,blesta expert -- 2

I need someone to completely modify whmcs on my server for me. I dont want it to work with normal domains but my own personal "domains." People will buy from me my "domains" and everything will work like the same as they are purchasing a normal domain but only from my reserve. In other words instead of checking for available domain on through icann or there contractors like godaddy to buy and domain and verify its available it will check against my database only. If this will be easier with github software like box that will be ok also to fork it and do this project. This will be a continuous job as business evolve. I am a coder but dont have time for that part as I am doing all other aspects. Budget is $100 BUT WILL OFFER MORE WORK ONCE SITE IS DONE.