There are lots of tool and guides available to help you on your business journey. Some have been created by specialist support services and are designed specifically for disabled people while others are more general business development guides.
Some are much harder to read than others but you should be able to find resources that suit you.
The RED guide to thinking about self employment.
Your business idea
Guide to working out a break even point
Easy read guide to writing a business plan from the Foundation for People with Learning Disabilities