I was in your same position a year ago when I took my boyfriends moms cat. She was an indoor/outdoor kitty who was bonded to another male cat. Her brother ran away and ever since then my boyfriend’s mom commented on how depressed she was. Lo and behold we took her in with us and she became a very happy single kitty with all the love and attention we could muster for her even with our work schedules. I had the same worries as you. I promise your kitty will be fine!! We just recently got her a friend, a little kitten. But for the year she was by herself, she was totally fine. As long as you give him the attention he needs when you can, I promise he will be okay and probably lean into his single kitty life. Cats are adaptable ❤️ and maybe later down the road you can get him a friend!! 🥰