Northfield, Minn., Code of Ordinances ch. 14, art. III § 14-115

(a) Generally. No dwelling, dwelling unit or rooming unit shall be let for occupancy to another which does not comply with the requirements of this article. All rental properties shall comply with the requirements of this article immediately upon the effective date of this article unless a different date or time is specified in this article.
(b) Compliance with applicable state codes. The structures on all rental properties shall be in compliance with the state building code and all related state codes which were in effect on the date such structures were constructed, added onto, altered, or repaired, or which otherwise apply by the terms of such state codes. If it is not possible or feasible to determine which code applied at the time of construction, addition, alteration, or repair, the least restrictive code provision which has existed at any time the structure has been in existence, or at any time an addition, alteration, or repair could have been made, shall apply. If a structure is found to be out of compliance with an applicable code, it shall be brought into compliance within a reasonable time following issuance of an order for correction, as determined by the building official.
(c) Northfield Property Maintenance Code. All rental properties shall comply with the provisions of the Northfield Property Maintenance Code, as stated in sections 12-21--12.23 of this Code. If a conflict exists between this article and the Northfield Property Maintenance Code, the most stringent requirements shall apply.
(d) Maintenance of safe and sanitary condition. Whether or not specifically mentioned in this article, all parts of all structures, accessory structures, appliances, equipment, systems, components, outside areas and other elements of all rental properties without limitation must be kept at all times in a safe and sanitary condition.
(e) Occupancy. The total number of occupants is to be determined by the building official and may not exceed twice the number of legal bedrooms plus one. Any bedroom which more than one person is to occupy must exceed the minimum 70 square foot habitable area by 30 square feet.