Ask HN: Is it possible to build successful SaaS company by outsourcing coding

I've been working on refining a SaaS product idea, I can build the web app part of the product but I cannot develop the mobile apps necessary. I thought it is a better approach to get the MVP build from an agency through continuous development process than hiring an in-house team for an idea that isn't validated yet. What do you think are the pros and cons of this approach? Are there examples of successful companies built this way? Please share your thoughts and experiences.