VPS for a startup backend

We’re preparing the backend infrastructure for a small startup and want to keep the initial setup simple. The application will use Node.js, PostgreSQL and a few background services.

Hostpro.com is currently one of the options we’re evaluating. Their KVM VPS plans with root access look attractive because we want complete control over the deployment environment without committing to a more expensive cloud setup.

For an early-stage product with unpredictable traffic, what VPS size would you consider a sensible starting point?