1. Safe entry and exit.
Everyone needs to be able to get in and out of the residence safely in case of an emergency. It's best to have at least 2 entries/exits for different escape routes. Maybe an accessible ramp or lift is required to avoid steps. We don't go up steps to enter the grocery store and we shouldn't need to go up steps to get into our homes. To achieve a 0-step entry there are a few ways to achieve this. One is to bring the grade up to door threshold using dirt then brick pavers or cement. For more than a few steps a lift in the garage is a good way to go. They are inconspicuous for security reasons, take up little space, and you can move them. Lumber or aluminum ramps are the least costly and if they have to be in the front yard they can be concealed with brick walls or creative landscaping. A low-profile door threshold should be installed with a 1/4'' height. Residential automatic door openers (entry, not garage), are wonderful and work for everyone - whether you're carrying a baby, groceries, or using a walker or wheelchair. They can be purchased and installed for as little as $1500. Make sure the lighting is good around the entryways and that the tenants can see through the peephole.
2. Next is a safe accessible bathroom.
Bathrooms are dangerous and slips and falls are the leading causes of injuries for elders. Bathtubs should be replaced with walk-in/roll-in showers. Enabling one to bath themselves by providing accommodations gives them a sense of independence and restores dignity. A 0-step barrier-free shower is best and works great for everyone whether you're hosing down your kid, taking a shower in a wheelchair or washing the dog - they're safer and add value to the home. A seat can be built in, installed and even mounted on a hinge so it folds out of the way. Install a dispenser for shampoo, conditioner and soap for ease of use and safety. Install grab bars around the perimeter and I always recommend a hand held shower spray with a holder that is mounted to a vertical grab bar. They meet the ADA weight bearing code and are much more durable. A shower wand with 69" long stainless hose will reach all the places required. A hot water scald guard will prevent burns.
3. Third is the kitchen.
Access to the kitchen sink is a must. Depending on the users a low-depth sink may be easier, and a good plan for wheelchair users. An easy to use faucet (maybe a pull-out) is a nice feature and again a hot water scald guard should be used. If the sink has an open vanity for wheelchair users a plumbing scald guard is required and very inexpensive. If you're considering new cabinets use vanity height for shorter users since their about 1-1/2'' lower. This will also allow the uppers to be lowered for easier reach. Pull-out shelves can be retro-fitted and eliminate reach problems. A raised dishwasher, approximately 8'', makes the job much easier and is another thing that's good for everyone. Good lighting is important as well as contrasting colors/shades around the kitchen surfaces. A pull-out shelf is great to have under an easy to reach microwave oven.
Remodeling the home with these universal designs can be a significant investment, but pales in comparison to hospital bills, and keeping our folks safe is priceless.
Reference: C. Thomas Wellington is a quadriplegic and advocate for accessible home remodeling for elderly and special needs community.