There's been a lot said and written abot the ethics rules in the House of Representatives this week. The Rules and guidance can be found in two main places - The Rules of the House themselves, especially
XXIII.— Code of Official Conduct
XXIV.— Limitations on Use of Official Funds
XXV.— Limitations on Outside Earned Income and Acceptance of Gifts
XXVI.— Financial Disclosure
XXVII.— Disclosure by Members and Staff of Employment Negotiations
In addition there is a large House Ethics Manual (456 pages in pdf!). A summary guide can be found here. CRS have produced a number of reports, including
House Committee on Ethics: A Brief History of its evolution and jurisdiction