Hummmmm, well it looks like a mismash. The Nixon, George H.W. Bush and Clinton librarys were built with private funds but receive federal funding for preserving and housing their archives. All the libraries charge an admission fee and have a gift shop to help defray operating cost. The 100 or so acres for President Reagan's library was donated by a wealthy California realtor. The George H.W. Bush library was built on the campus in College Station. And, Bubba's has a tiein with the University of Arkansas so I expect they are picking up part of the tab for his. Back in the mid 80's Congress pass a bill or an amendment that required libraries larger than a designated square footage (50 or 60,000 sq ft, I think it was) to be endowed. If I'm not mistaken, the Reagan Library is about 150,000 sq ft. The endowments are created by private foundations who raise money from the president's political supporters.