President Biden and his family, including disgraced first son Hunter, are spending their summer vacation at a $20 million beachfront mansion in South Carolina, The Post has learned — and they’re not paying a dime. The president recently asked prominent Democratic donor Maria Allwin — the widow of hedge fund founder James Allwin — if he could stay at her nine-bedroom Kiawah Island estate, a source close to the family told The Post. “They stayed here before and they’re not paying,” the source said. “They’ve never paid. They’re just friends.”
