What are the best exercises for someone (54 year old male) with low back pain, knee pain

What are the best strength exercises for someone (54 year old male) with low back pain and knee pain? This person is pre-hypertensive and has a BMIi of 39. Wants to lose quite a bit of weight and has never lifted weights before. Any suggestions on some exercises to be prescribed? (legs, core, back….). I don’t want to overwhelm him with too much.. since he has never lifted. How many reps and sets are appropriate for this client?… (8-12, obviously low weight… perhaps 2 sets? Thanks so much!