You will have to evaluate what will be a better source of income: a business… or Fiverr? If you want to work with this other person you will have to share contact details, which would either get a strike against/or suspend your Fiverr account. But 50/50 is a LOT. If I were you, I would keep the business for myself and for marketing, employ a director. Not share half of your profits with them. But before making any decision, you will have to do a LOT of research about business and marketing.