Currently, while storefronts, public areas and public bathrooms must legally take measures to accommodate everyone with disabilities, online ADA compliance is not mandatory on anything but government-managed websites. Instead, these rules act as guidelines to ensure that disabled people have the same ability to access and read/view your website as everyone else.
ADA compliance isn’t a set-it-and-forget-it thing. Compliance standards must be followed and will evolve just as your website does. There are guidelines all website contributors must know to stay within ADA guidelines. It is generally not burdensome but it does require some web managers to change their workflows. For example, loading images up to your ecommerce site will always need some of that alternative text (alt tags) mentioned above.
If those together don’t make the opening big enough, it might be possible to reconstruct the whole doorway and door, depending on the construction of the building. I rebuilt one doorway in my own home and it only cost around $1,000-$1500 – and that was using a very high end contractor. It was also wood frame construction and drywall, in a non-bearing wall; you’ll have a different scenario, of course, with steel, or with masonry, and/or plaster and lathe, and if it’s a bearing wall. 

Decided by the US Supreme Court in 2002, this case [74][75] held that even requests for accommodation that might seem reasonable on their face, e.g., a transfer to a different position, can be rendered unreasonable because it would require a violation of the company's seniority system. While the court held that, in general, a violation of a seniority system renders an otherwise reasonable accommodation unreasonable, a plaintiff can present evidence that, despite the seniority system, the accommodation is reasonable in the specific case at hand, e.g., the plaintiff could offer evidence that the seniority system is so often disregarded that another exception wouldn't make a difference.

An "adaptable dwelling unit" is a dwelling unit in a building with a building entrance on an accessible route designed in such a manner that the public and common use areas are readily accessible to and usable by a person with a disability, and all doors are designed sufficiently wide to allow passage into and within all premises by persons who use wheelchairs as required by the building code.

The lack of regulations here has led to the absolute worst-case scenario. People with disabilities have not been served since most companies are unaware this is an issue. Most don’t even realize this is something they have to consider until they receive a demand letter. That has certainly been the case for some of my clients. This leads to a scramble to get compliant. Unfortunately, it can take up to a year to do so depending on the complexity of the site. Meanwhile, plaintiffs’ attorneys across the country are taking advantage of the confusion. More than 260 website accessibility lawsuits were filed in 2016, and significantly more were filed by the end of 2017. But these numbers do not even begin to cover the cases that are settled pre-litigation.