The Missouri Department of Health & Senior Services licenses Assisted Living Facilities, Intermediate Care Facilities, Residential Care Facilities, and Skilled Nursing Facilities.

Reference: Laws, Regulations & Manuals | Nursing Homes & Other Care Options | Health & Senior Services (mo.gov)

Summary: The limit appears to be two (2) individuals not related to the operator.

From MO Title XII Public Health and Welfare, Chapter 198.006:

• Assisted living facility, any premises, other than a residential care facility, intermediate care facility, or skilled nursing facility, that is utilized by its owner, operator, or manager to provide twenty-four-hour care and services and protective oversight to three or more residents who are provided with shelter, board, and who may need and are provided with the following:
  (a)  Assistance with any activities of daily living and any instrumental activities of daily living;
  (b)  Storage, distribution, or administration of medications; and
  (c)  Supervision of health care under the direction of a licensed physician, provided that such services are consistent with a social model of care;
• Intermediate care facility, any premises, other than a residential care facility, assisted living facility, or skilled nursing facility, which is utilized by its owner, operator, or manager to provide twenty-four-hour accommodation, board, personal care, and basic health and nursing care services under the daily supervision of a licensed nurse and under the direction of a licensed physician to three or more residents dependent for care and supervision and who are not related within the fourth degree of consanguinity or affinity to the owner, operator or manager of the facility;
• Residential care facility, any premises, other than an assisted living facility, intermediate care facility, or skilled nursing facility, which is utilized by its owner, operator or manager to provide twenty-four-hour care to three or more residents, who are not related within the fourth degree of consanguinity or affinity to the owner, operator, or manager of the facility and who need or are provided with shelter, board, and with protective oversight, which may include storage and distribution or administration of medications and care during short-term illness or recuperation, except that, for purposes of receiving supplemental welfare assistance payments under section 208.030, only any residential care facility licensed as a residential care facility II immediately prior to August 28, 2006, and that continues to meet such licensure requirements for a residential care facility II licensed immediately prior to August 28, 2006, shall continue to receive after August 28, 2006, the payment amount allocated immediately prior to August 28, 2006, for a residential care facility II under section 208.030;­­
• Skilled nursing facility, any premises, other than a residential care facility, an assisted living facility, or an intermediate care facility, which is utilized by its owner, operator or manager to provide for twenty-four-hour accommodation, board and skilled nursing care and treatment services to at least three residents who are not related within the fourth degree of consanguinity or affinity to the owner, operator or manager of the facility.  Skilled nursing care and treatment services are those services commonly performed by or under the supervision of a registered professional nurse for individuals requiring twenty-four-hours-a-day care by licensed nursing personnel including acts of observation, care and counsel of the aged, ill, injured or infirm, the administration of medications and treatments as prescribed by a licensed physician or dentist, and other nursing functions requiring substantial specialized judgment and skill;