Resistance bands are stretchy, OP. Like big elastic bands. You pull against the stretch, with one end held stationary; different bands are different levels of stretchy, so the exercises can be altered in intensity depending on how much elastic band you allow yourself, and how easy it is to stretch it.
TRX/suspension trainers (TRX itself is very expensive and no better than many of the cheaper alternatives, but make sure that what you buy fixes over a door, if he's a homebody) are essentially just a flat rope with a split, and handles with a length 'slider'. You hook it over the door, set it to the right length, for, say, press ups or pull ups, and it's as if you have a bar there to lean on or hang off. You adjust the exercise intensity by moving your body position (for example, a horizontal press up is much harder than a nearly-standing one)
I'd say that if you want to do 10 exercises, you'll probably need a variety of resistance bands, but you'd only need 1 TRX/resistance trainer.
Lots of pull up bars can be put up/taken down per use, and don't need any fixings. www.amazon.co.uk/TUOKE-Leverage-Strength-Training-Equipment/dp/B0965TFQ28/?tag=mumsnetforu03-21
I'm really into the idea of working out at home, as you can probably tell! This sort of thing makes changing the weight you're using much easier (just flick a switch and it picks up the right amount, rather than screwing them on and off, and leaving them scattered all over the floor)
www.amazon.co.uk/CENSUNG-Adjustable-Dumbbells-Increased-Training/dp/B08YN9BJK8?tag=mumsnetforu03-21