"Release your idea into the market. See how it is being adapted. Then take the decision to invest time and energy in building a complete system around your idea."
This is the suggestion I usually give to my clients, particularly to the boot-strapped start-ups. Starting small, only with the core features, and releasing to the audience as v1 is what is usually termed as an MVP (Minimum Viable Product).
Once an MVP is validated, clients can then focus on rebuilding the platform from scratch for the holistic vision of the idea keeping in mind for scalability, reliability and security.
WordPress fits best for MVP needs. Apart from the out-of-the-box features such as the various content types, WordPress is supported by robust e-commerce features with payment integrations, readily available themes, newsletter integrations, analytics tools to measure traffic and conversion rates, and smart forms solutions.
MVP also makes senses for a project with a huge scope. Slicing the project's scope into smaller chunks with iterative releases. The first release focus in this case always is to have core features out for the users.
When MVP doesn't work -
Read – http://sethgodin.typepad.com/seths_blog/2011/11/when-minimal-viable-product-doesnt-work.html