Protecting Our Students and Taxpayers Act of 2017 or the POST Act of 2017 This bill amends the Higher Education Act of 1965 (HEA) to modify requirements for a proprietary (i.e., for-profit) institution of higher education (IHE) to participate in title IV (Student Assistance) federal student aid programs. Current law requires a proprietary IHE to derive at least 10% of its revenue from sources other than title IV federal student aid. This legislation requires a proprietary IHE to derive at least 15% of its revenue from sources other than federal funds (i.e., it replaces the so-called 90/10 rule with an 85/15 rule). It defines federal funds to mean title IV federal student aid, as well as education benefits for military personnel and veterans. Additionally, the bill limits what a proprietary institution may treat as revenue to the school in calculating whether it derives at least 15% of its revenue from sources other than federal funds. Finally, the bill moves the 85/15 rule from title IV to title I (General Provisions) of the HEA, making compliance a condition of institutional eligibility to participate in title IV federal student aid programs (i.e., failure to comply results in immediate loss of institutional eligibility). Currently, a proprietary IHE must violate the rule for two consecutive years before losing eligibility for title IV programs.