Application timeline masters in biology

Son is in his senior year at a UC and has had a junior scientist job at a biotech company since freshman year. They like him and he loves his work but it’s not certain if they’ll have a full time spot for him when he graduates. His preference would be to take a break from academics and work for a year or two before perhaps going for a masters. I wonder, if May comes and they don’t have a spot for him - what’s the shortest time to get into a graduate program and start it? That is, could he apply in May and start working his masters in January? Or is the application cycle akin to applying for undergradate with an application in the fall, spring acceptance and start in the following fall? His undergrad major is Bio with Bioinformatics concentration. Likely cum laude or magna cum laude.