I've got everything necessary for a compound lift programme at mine but we'll likely be putting together a gym at his with what we need as we need it. It's a farm so we might build a rack etc. Machines are basically out of the picture, free weights, bands etc are likely and that's how I train so I can help with the form the best in those modalities.
His experience is zero, he as far as I know has never played a sport or game in his life, but he started building his own house in his 60's and whilst I did most the heavy lifting he's always been a second in the two person lifts. Diet is focused on calorie restriction to maintain lower weight, but is pretty good and Mediterranean, sleep habits good.
Once he decides on something being the right way forwards he does it, it'll not be an issue to maintain a schedule or diet etc. The main problem was the cultural shift and that's happened.
Edit: the illness was tuberculosis and I believe part of the calf was destroyed by it. There's no pain in use and it responds to training, it's just that he's favored the good leg his entire life. No joint issues in the slightest (bastard).
Part of the calf destroyed as a result of TB? I've heard that TB can cause nerve damage, but don't know much about it. Anyway.
Man, good diet, good sleeping habits and no joint pain at 75? That's crazy, good for him.
Alright, it sounds like it's a pretty good starting point, but still take precautions. Don't let him "soldier" through stuff that's unsafe or rush him into heavy loading. It's hard to know exactly what he needs because well, we don't know him and can't see him in person. With that said, some general guidelines for training the geriatric/elderly.
Make it as comfortable and safe as possible to begin with. Meaning, stable exercises. You might need to make a lot of regressions initially to find a reasonable training level. That's why machines are a great way to ease into a training routine. It's safe and you have complete control, plus you can focus on improving muscle size and strength in isolation. There's also plenty of evidence to show that machine training improves functional outcomes like balance and daily activities in geriatric "patients". If that's not an option, you
can do without. Going further:
1. Make sure to warm up properly and get the joints moving. General joint movement is severely underrated, especially for the elderly. Basic stuff, small hip circles, painfree reaches, shoulder circles, getting loose. Don't make it into "hardcore" mobility drilling, keep it pain free.
2. Take advantage of isolated exercises, sitting down, using a bench or being on the floor to preserve energy and have better control. Glute bridges, posterior tilting of the pelvis with ab contractions, clam exercise with bands, external shoulder rotations with bands, pushups on knees if possible (put something under knees to cushion) or pushups against a windowpane standing to change the angle and make it even easier (besides that you have to stand), so on.
3. Use isometrics and take advantage of eccentrics when you can. Isometrrics are extremely valuable here because you can create tension without using big ROM or high loads. It also helps with teaching him to active his muscles. Helps with co-contractions too, meaning hopefully activating ALL the muscles supporting the joint. In regards to eccentrics, as you age you cannot produce the same amount of force and velocity during concentric contractions, however eccentrics have the inherent benefit of increasing muscle tension and force during elongation. Important disclaimer with this, I would mostly use eccentrics during isolation exercises to begin with as it's easier to control and the balance requirements are not as limiting. Also, eccentrics cause greater DOMS which is important to be aware of. DOMS are killers at that age which is why you need to be diligent about GRADUALLY increasing the load over time. Don't go too fast.
4. Make compounds and basic movements easier. In that regard Oblivian gave good advice. Don't let him lift off the floor, use blocks. Better yet, practice the movement with a kettlebell or bag first before moving on. Same with squats. Start with maybe quarter BW squats with isometric holds. Move on to perhaps light goblet squats. Depending on his level. Then box squats or quarter/half squats with a safety bar if possible. Again, it all depends on where he's at and how he responds. You can use a chair as well and just do sit to stands. Here you can slightly pull the leg that you want him to work more on closer to his body. This will force him to put more weight on that leg when standing up. HOWEVER, I wouldn't focus too much on unilatal work to begin with, unless it's during isolation exercises. Just focus on having a well balanced weight distribution while doing the exercises as this will help reduce the imbalance, and give him a chance to get used to them.
5. To reiterate, make it "comfortable" and make it safe. He's not trying to be a world class athlete here. Be prepared to switch things around or regress exercises if needed. Higher blocks, higher box, less ROM, less weight, different exercise so on.
Start slow and keep us updated! He's going to be learning a lot of new stuff so cut him some slack. I'd like to give more feedback depending on what you decide for him and how it goes!