With recreational marijuana sales set to begin Jan. 1 in Illinois, the nascent industry is readying for what’s predicted to be strong consumer demand. Growing facilities are expanding, and companies need to hire people to staff those locations as well as stores. Some 5,800 people already work in the industry in Illinois and within a year, employment could swell to more than 13,500 jobs, according to New Frontier Data, a Washington, D.C.-based firm that provides analysis and figures for the cannabis industry.