There's a lot of things, the first most important is widening your doorways to 36". Have wide, clear pathways thru the house. Renovate bathrooms for curbless shower, a wash bowl without vanity and a taller toilet. In kitchen have more drawers than doors. Install a drawer microwave in base cabinet. For a complete make over, call your local ADA division of government, they can send out someone to assist you.
Entrances are one area where those in wheelchairs have trouble. Getting into your home will probably require a ramp. In order to propel oneself up a ramp the ADA recommends no more than 1" of rise for every foot of run. If your threshold is 36" above ground level, you will need 36 ft of ramp with a level area at top and bottom of 5 ft. You may have to build a deck platform on top of the porch to provide for level and turnaround area. Ramps longer than 30 ft must have a level resting area between the top and bottom. Wheelchair ramps must have railings even if the ramp height is less than 30" above the ground.
Doors less than 32" wide are too narrow for a wheelchair; 36" is recommended. While 36" is the minimum width for a hallway, if a door is at a hallway end and perpendicular to the hallway, more room may be needed to allow the wheelchair to turn. Thresholds can also be a problem as the bump can cause significant resistance, especially for a person with reduced strength. The following link talks about these and other problems, and provides solutions: https://www.southbayresidential.com/wheelchair-accessible-home-modifications.php
Wheelchairs usually require a 5' space in which to make turns, so keep this in mind for bathrooms, hallways, bedrooms. A two story home will require an elevator or stair lift, assuming the person can transfer.
Piping below sinks should be covered to preclude burns. Hot water temps need turned down to 120° or lower.
Front loading washer dryer will be needed if the person will do their own laundry.
Grab bars may be needed in hallways, but must be installed in the shower and toilet areas. A hand held shower wand would be helpful.
Motion activated lights would be helpful.
Flooring materials should be evaluated, as some surface materials make it much more difficult to move a wheelchair.
Contact your local ADA chapter to help you out. Here are some guidelines to get you started.
Thank you all, however contact info applies to U.S. I am in Canada, am greatful for all the information