Do you posses a specific skill-set? It could be anything from sharing legal advice, informing businesses on how to become more eco-friendly, or assisting startups on how to get off the ground. Consulting or coaching can be a lucrative side business since it's easy and affordable to start, since you already have the knowledge and experience. And you can build your own schedule so that you can offer your consulting services whenever you have the free time.
For anyone who has capped at their current job, it could be time to look for another. If your salary is capped, it typically means that you are an expert for your current job, and the company can’t pay you anymore money for doing the same job. Take this as a sign to better utilize your skills at a more challenging, and subsequently higher paying job.