Can anyone design or remodel a homeowners home to accommodate aging person or compensate for any disability?

My friend wantsstart a small business to paint exterior and interiors of homes, and make small changes or updates to made the homesowners home more disability or aging more comfortable/ and accessible? Such as wider doorways and lower kitchen sinks, build wheelchair ramps.(Texas)

he must be licensed to do any work for the disabled! he could be sued big time he someone gets hurt