If he is just starting out and looking to do just a 3 times a week maybe a Push Pull Legs routine would be good. Although it may be a little more beneficial to do full body both days. I will give you pros and cons of each and make a customize routine for only 30 minutes a routine.
Push Pull Legs
Pros - This will allow him to really focus on certain muscle groups and build strength relatively quickly.
Cons - He will be more sore with this routine than the other (most likely) because it will work the muscles more, but less muscles every workout. It will also not maximize his protein sythesis.
Full Body 3x A Week
Pros - Will allow him to work all muscles enough to stimualte growth and developement, as well as maximize the protein synthesis.
Cons - His whole body will be sore (not too sore) the next day. Will not be able focus on individual muscle groups, but just compound movements.
Personally I would suggest maybe a month of full body work outs then after that progress to Push Pull Legs, and if he doesn;t get a bigger benefeit then maybe return to the Full Body split, but it is up to you and him.
Push Pull Legs Routine
Day 1
Bench Press 3 sets 10 reps 1 minute rest between sets
Keep it realtively light weight he shouldn't struggle too much because he just needs to get his mechanical strength down at first, after he is able to do his starting weight for a long period of time progress him very slighty (10-15%)
Dumbell Shoudler Press 3 sets 10 reps 1 minute rest between sets
Same as the bench press
Overhead Tricep Extension 3 sets of 12 reps 1 minute rest between sets
On this don't let him go too heavy, just let him get the general movement to get blood flowing into his triceps because they will already be fatigued greatly from the first two excercises. He just needs blood flow to help nutrients get to his muscles.
Dumbell Fly 3 sets of 12 reps 1 minute rest between sets
Same as the Tricep Extension, just let him get some blood flow and work on contracting his pecs. Watch him very closely to make sure he isn't injuring his shoulders, if you can use cables or a machine that would be good. Buying a cheap pair of resistance bands can help with this at home.
Dumbbell Lateral Raises 3 sets of 12 reps 1 minute rest between sets
Same as the fly
Day 2
Barbell Row 3 sets of 10 reps 1 minute rest between sets
Same thing here as the Bench press above, but make sure he isnot slouching when he performs this movement or he can injure himself.
Pullups 3 sets of 10 reps 1 minute rest between sets
If not able to perform reps do 3 sets of as many as possible, once 10 becomes easy use some weight.
Dumbbell Bicep Curls 3 sets of 12 reps 1 minute rest between sets
Keep it lightweight and just makeh im focus on his squeeze.
Dumbbell Pullover 3 sets of 12 reps 1 minute rest between sets
Keep it light and make him try to focus on using his back and not his chest.
Preacher Curl 3 sets of 12 reps 1 minute rest between sets
Same thing as the dumbbell bicep curls.
Day 3
Squats 3 sets of 10 reps 1 minute rest between sets
Same thing as the Bench Press
Dumbbell Weighted Lunges 3 sets of 10 reps 1 minute rest between sets
Make sure he is going all the way down and pausing, and exploding out from the bottom.
Goblet Squats 3 sets of 12 reps 1 minute rest between sets
Keep this light at first because it will be tough on joints at first. Allow him to just keep a straight back, and if possible use a seat to perform these like a "box squat".
Leg Extensions 3 sets of 12 reps 1 minute rest between sets
Keep these light and just get the blood flowing like the tricep extensions above.
Leg Curls 3 sets of 12 reps 1 minute rest between sets
Same as the Leg Extensions
Full Body Routine 3x a week
Bench Press 3 sets 10 reps 1 minute rest between sets
Keep it realtively light weight he shouldn't struggle too much because he just needs to get his mechanical strength down at first, after he is able to do his starting weight for a long period of time progress him very slighty (10-15%)
Barbell Row 3 sets of 10 reps 1 minute rest between sets
Same thing here as the Bench press above, but make sure he isnot slouching when he performs this movement or he can injure himself.
Squats 3 sets of 10 reps 1 minute rest between sets
Same thing as the Bench Press
Dumbell Shoudler Press 3 sets 10 reps 1 minute rest between sets
Same as the bench press
Pullups 3 sets of 10 reps 1 minute rest between sets
If not able to perform reps do 3 sets of as many as possible, once 10 becomes easy use some weight.
Dumbbell Weighted Lunges 3 sets of 10 reps 1 minute rest between sets
Make sure he is going all the way down and pausing, and exploding out from the bottom.