Any persons, natural or artificial, including domestic and foreign corporations, lending money in this state, to be paid back in monthly or weekly installments, may charge interest thereon at the rate of seven percent (7%) per annum or less, unless otherwise specifically authorized by law, for the entire period of the loan, and aggregate the principal and interest for the entire period of the loan, and divide the same into monthly or weekly installments, and may take security therefor by mortgage, deed of trust, or title, with waiver of exemption, upon and to real estate or personal property, or both.