The ADA requires businesses to remove barriers overnight. Businesses are only required to do what is readily achievable at that time. A small business may find that installing a ramp is not readily achievable this year, but if profits improve it will be readily achievable next year. Businesses are encouraged to evaluate their facilities and develop a long-term plan for barrier removal that is commensurate with their resources. Restaurants must provide menus in braille.
Waiters can read the menu to blind customers.
The ADA requires extensive renovation of all state and local government buildings to make them accessible. Local governments have been subject to this requirement for many years under the Rehabilitation Act of 1973. Not every building, nor each part of every building needs to be accessible. Structural modifications are required only when there is no alternative available for providing program access. Let's say a town library has an inaccessible second floor.