A district may take by grant, purchase, gift, devise, or lease, or condemn in proceedings under eminent domain, or otherwise acquire, and hold and enjoy, real and personal property of every kind within or without the district necessary to the full or convenient exercise of its powers. The board may lease, mortgage, sell, or otherwise dispose of any real or personal property within or without the district when in its judgment it is for the best interests of the district so to do. The provisions of this section apply to all sales or mortgages heretofore or hereafter made.