What is the typical implementation time and resources (Internal & External) required to migrate to a SaaS ERP platform?

This question is best answered if some context is available (e.g. what functionality is being implemented, how much process re-design is needed, how many locations (any foreign currency/language), number of users to train, your desired timeline, etc.

But here are some examples we've managed:
1. For a billion dollar global corporation, we went live in 5 countries within 6 weeks of signing the SaaS contract; 51 countries within 9 months; that required 3 of us in the PMO, plus client staff (say average of 5 functional people for 25-33% of their time, no IT involvement).
2. For a $75 million single local operation, we went live within 7 weeks of starting the implementation; one consultant, plus the controller about 33% of the time.
3. For a smaller internet retailer, we helped them go live over a period of about 3 months; 0.25 consultant, plus the controller about 33% of his time.

On the SaaS vendor side, you may see one or two consultants face to face, but behind them at their development/customer service centers, there are often support staff who help with configuration, server set up - you don't see them.

Remember, what really is different about SaaS implementation (assuming you have chosen the best fit package for your business) is the avoidance of IT hardware and system set up. That means you can get started far quicker. However, you still need to determine your future processes, make design/ configuration decisions, test and migrate, manage the project and address change management factors.