With regards to this quote:
even if the relationship between a Bahá’í man and woman is entirely innocent, it is vitally important that they should not live together in a way that would give the wrong impression. If there is any doubt about the perceived morality of a particular situation they should unhesitatingly avoid it and seek alternative arrangements in order to preserve the good name of the Faith. In following the standards of the Faith, the friends must be not only righteous, but also wise. Naivete can do great harm, especially in the present unstable condition of social morals in the world at large. (Universal House of Justice, 12 September 2000)
Here is a comment by the USNSA - - - -
Although it is no longer uncommon among the population at large in the United States for unmarried individuals of the opposite sex to share living arrangements, such arrangements are not in keeping with the high standards and moral expectations of the Bahá’í teachings. The National Assembly feels that, even when such arrangements maintain a purely economic character, they may still create an appearance of immorality or moral laxity that adversely affects the reputation of the Bahá’í Faith and its teachings. Although, generally speaking, unmarried Bahá’ís should not live in one house with members of the opposite sex who are unrelated to them, it is up to the Local Spiritual Assembly in whose area of jurisdiction the individuals are living to determine, on a case-by-case basis, whether or not a given living situation creates an appearance of immorality.
and by the UKNSA - - - -
"With regard to mixed sex accommodation, in general, the National Spiritual Assembly understands the situation of people of opposite sexes who share accommodation for financial or other practical reasons. In these somewhat dangerous times, it is even sometimes advisable for a group of young women to share accommodation with young men as a protection against intruders and those who might threaten them, providing, of course, that they are clearly accommodated in separate bedrooms and there is no suggestion that there is a sexual relationship among them. Each situation has to be treated on its own merits, case by case. The Local Assembly must be satisfied that there is no wrong-doing on the part of the parties or the appearance of this. If the situation is bringing the Faith into disrepute, then the Local Assembly must deal with it appropriately.