Planning to start a saas startup as a dev!

For a beginner with full-stack development knowledge planning to start a SaaS startup, what advice would you offer to avoid falling into the 90% of SaaS ventures that fail? The individual faces unique challenges, being differently-abled and reliant on a wheelchair. They intend to build the startup entirely on their own, with no friends or family support. Considering this situation, what struggles might they encounter, and in which areas would external help be essential to ensure a successful launch? Suggestions or advice on navigating these challenges would be greatly appreciated.