In his first business, Caremark, Sweeney sought and received backing from the prestigious Silicon Valley venture capital firm, Kleiner, Perkins, Caufield, and Byers.

In all, he successfully took four companies public, led a Leveraged Buyout Organization (LBO) resulting in a 650% return to investors and 77% IRR in less than four years, raised over $2 billion in financing for his various companies including $500 million in venture capital, $700 million in debt financing and $400 million in two IPOs. The $2 billion invested resulted in $30 billion exit value.

For decades, he has been involved in buying, selling, or taking public many healthcare companies.