Section 18. Whether or not an operating agency has been created therein any city or town may undertake, itself or by or through any department, board, agency, authority, or office of the city or town, or by or through any operating agency, planning district, metropolitan district, or other public body any planning activities within such city or town for the preparation or completion of master or general plans, a workable program for development of the community, general neighborhood renewal plans, a community renewal project, any other planning study, project or program and a code enforcement project, including the voluntary or compulsory repair and rehabilitation of buildings and improvements, the enforcement of laws, codes and regulations relating to the use of land and the use and occupancy of buildings and improvements, and the provision and repair of streets, curbs, sidewalks, street lighting, tree planting and similar improvements in connection therewith and may authorize such department, board, agency, authority, office, operating agency, district or public body to act as the agent of such city or town in entering contracts for financial assistance for such purposes from the federal government or the commonwealth. Any such city or town may raise and appropriate or agree with such department, board, agency, authority, office, district, operating agency or public body or with the federal government or the commonwealth to raise and appropriate such sums as may be necessary for the purpose.