The board of supervisors of a county shall not adopt any resolution authorized by §§ 36-40, 36-41 or 36-42 unless a public hearing has first been held. The clerk of such county shall give notice of the time, place, and purpose of the public hearing at least seven days prior to the day on which the hearing is to be held, in a newspaper published in such county, or if there is no newspaper published in such county, then in a newspaper published in the Commonwealth and having a general circulation in such county. Upon the date fixed for such public hearing an opportunity to be heard shall be granted to all residents of such county and to all other interested persons. In determining whether dwelling accommodations are unsafe or insanitary the board of supervisors of a county shall take into consideration the safety and sanitation of dwellings, the light and air space available to the inhabitants of such dwellings, the degree of overcrowding, the size and arrangement of the rooms and the extent to which conditions exist in such dwellings which endanger life or property by fire or other causes. In connection with the issuance of bonds or the incurring of other obligations, a regional housing authority may covenant as to limitations on its right to adopt resolutions relating to the increase or decrease of its area of operation.