There are plenty of low cost options that will help cleanse his kidneys and flush the liver.
Parsley. You can use fresh. Or, use dried herbs. I used dried herbs and my kidney pushed out little grains of grit.
Watermelon. A well known kidney cleanser. He can grind up the seeds to make a kidney cleansing tea
Celery Seed. Not as strong as parsley or watermelon. May be a better option until his kidneys become healthier
Most people start off doing the HC Liver Flush (Olive Oil, Citrus Juice and the ES Cocktail). There is a gentle option that Plzchuckle (she's a very informative source in the Liver Flush Forum ) is using. The HC Flush can be very harsh for someone that has a lot of toxins and very little mineral reserves
Detox Baths: OMG, these are wonderful. Relaxing. Will help remove toxins from the skin. All of the ingredients can be purchased from the grocery or drug store.
I would look into introducing him to an alkalizing diet. Eating fruits, veggies, minimal protein, healthy fats, no processed goods. He will need to play around with his diet before he figures out what is best for him. For me, grains and cow dairy are a no no. Mineral rich foods like Blackstrap molasses (which shouldn't affect his diabetes), Apple Cider Vinegar, Kelp will be beneficial for him. He might want to review askmoreless.com or go to the Ask Moreless Forum and read all of the information. He doesn't have to do the "drink" or he can modify if one of the ingredients makes him uncomfortable. Some people have issues with the calcium hydroxide (pickling lime water). Some use other forms of calcium. Definitely read everything. I learned a lot over there.
Having a good amount of minerals reserved will make the Liver Flushing easier to handle. The body is going to release a large amount of toxins. People get sick when they don't have enough alkaline minerals to deal with the acidic toxins being released. He should make sure his bowels are clean.
Barefoot Herbalist is also a helpful forum. If he decides to introduce herbs into his health regimen, you can learn alot over there. I did.
Go to orthomolecular.org and whfoods.com to learn more about how WHOLE FOODS can heal. These sites is a god send and has tons of information. It explains the importance and purpose of every mineral, vitamin and oil are bodies need.