Working as a freelance writer is different from looking for work as an employee. You are sending pitches out or applying for gigs as a contractor. Where I live, an employer is required to provide accommodations for employees with disabilities, up to the point of extreme hardship. Contractors don’t have this level of protection.
I believe that clients care about whether a particular freelancer can do the work that has been assigned, and turn it in by the deadline more than if the person they have hired has a disability or lives with a chronic condition. If you work remotely, you and your client may never be in the same room together. The fact that you have challenges or need to use assistive devices is not apparent to the client, unless you choose to reveal that information.
Is it ever a good idea to share this kind of personal detail with a client? Most of the time, I would say that you should keep it to yourself, but there are times when you should reveal it. If you applying for a gig or making a pitch where personal experience with the illness or disability will make you a better candidate, then it’s appropriate to include the information in your cover letter.
Another situation where you may want to consider sharing details about your health with a client may be where you have a well-established relationship and you need to either rearrange your schedule or take some time off. Most clients will be very understanding if you let them know what is going on.
The level of detail you provide will depend on your relationship with the client and your own comfort level with discussing your condition. A simple statement that you will be away because of an appointment but will complete your assignment by X date may be sufficient. If you need to book some time off, tell the client. If you need to be away for an extended time, you may want to offer to find a writer you can subcontract your work to until you are able to return.
Living with a disability or a chronic health condition doesn’t mean you can’t have a successful freelance writing career. While you may not necessarily have to reveal this information to everyone you work with, in some cases you may choose to share it with your clients.