Community Mortgage Lender Regulatory Act of 2017 This bill amends the Consumer Financial Protection Act of 2010 to specify that the Consumer Financial Protection Bureau (CFPB) may audit, investigate, or take an enforcement action against a responsible community mortgage lender other than a depository institution or credit union, but only if requested to do so by one of several specified regulators or agencies. A "responsible community mortgage lender" is one that: (1) meets certain restrictions with respect to number and volume of mortgage loan originations and amount of either assets or net worth; and (2) has not, with respect to its mortgage loan originations and within a specified time frame, been subject to a cease and desist order or found by a court to have violated the law. Furthermore, the CFPB and other federal banking agencies are prohibited from requiring such a lender to audit one of its vendors or third-party contractors unless the CFPB or other agency has reasonable cause to believe that the vendor or contractor is causing the lender to violate the law.