As Dan has rightly pointed out, you need to be able to put together a clear and a detailed specification of the SaaS product you need.
I understand that as someone who has a great idea, there is a very strong urge to get started and get it done as quickly as possible. The challenge is the technical team's thought process is not aligned with your because they come from a different world (as in they do not really know your domain yet).
This is how I would recommend approaching it.
- A detailed requirement specification cannot be written overnight or in say 2 - 3 days. In my experience, it could take anywhere between 1 - 3 weeks depending on the complexity of the application, the integration points with existing systems etc.
- Once you are done, I would suggest you share it with two people who you believe understand the idea. Their job is to poke holes in the specification you have drafted. They would identify loop holes in the user flow, they would uncover certain assumptions and much more.
- After a brainstorming session, you would need about a week to put everything together again.
- With this specification in hand, you can start looking for agencies who can build it for you. I am recommending working with an agency because putting together a team with a technical manager, programmers, testers and a UI/UX designer is a large project in itself.
- When choosing an agency, I would recommend picking an agency that can provide solutions in PHP / RubyOnRails / Python / Java. Technology is usually not a concern (unless you are building a bank transaction or a guided missile system) if the system design and architecture is good.
- Ask for estimates (time and cost) from say top 3 agencies you select. Have a clause where you receive a discount if the deadlines are not met.
- Plan 2 week milestones with the agency you choose, and monitor. With a good agency, if the specifications are clear and changes introduced during the process are not more than 20%, it should be smooth sailing.
- The implementation phase would include User Experience (UX) design, User Interface (UI) development, backend programming, testing and so on.
Approach for Writing Specifications
Writing requirement specifications does not require any technical skills. It can be all in plain simple English and there would always be some gray areas.
- Identify the roles in the system. User, Admin, Staff etc.
- Identify what would you want each one of them to do.
- User Registration
- Search etc.
Identify areas of interaction between the roles of the system. Can an Admin block a user? etc.
Identify at which points would the existing system integrate with this new application. What data would be fetched from the existing systems and how should it be processed and what would be the result.
You would also have to identify the corner case scenarios in the system.
If you are interested I can send over a draft of user requirements.
The agency you pick should have experience working with startups and team of 2 - 3 co-founders. They should also believe in the idea and have a strong sense of ownership. A team that would view this engagement as just another project would not be fun to work with.