@Mr_NutterButter @LukeAlmighty You can get decently far with bodyweight exercises, but if you want to get far with it, you will of course need to spend a lot of time on it.

Something that doesn't require more than twenty to thirty minutes per day, and probably a lot less once you get into the routine, is the following:
A good "goal" for beginners to aim for, in my own beginner-mind and if you do not go to the gym, is to do fifteen to twenty pushups, fifty squats or lunges, and fifty situps. Doing this two times per day, every day, will set a good standard. As for the two times per day, I'd say morning when getting out of bed, afternoon when coming home from work and evening before going to bed are ideal times to get to it, because those are moments where you are not in the middle of doing something else.
If you cannot do the full number of repetitions, then that's alright. Just do as many as you can, and aim to increase your performance every month.