This page explains some rules for family members who want to apply to stay in or come to the United Kingdom if you are applying under the investor category (Tier 1 Investor) of the points-based system to come to the United Kingdom.
Your dependants are allowed to work, though your partner may not be allowed to work as a doctor in training.
Dependants may not switch into any points-based system tier in their own right.
If your dependants later want to be in the United Kingdom under the points-based system in their own right, they will have to leave the United Kingdom and apply for entry clearance.