If you were 28 with my background, what business would you build today?

I’m 28, based in Toronto, Canada, and I’m looking for advice from people who have already built something of their own.
My background is a Bachelor’s in Architecture, followed by a postgraduate degree in Project Management. I started my career in architecture before moving into project management, and today I’m earning around $100k/year.
From what I can see, I could continue climbing the corporate ladder and probably reach the $150k–160k range over time. That’s great, but I don’t think my long-term goal is to remain an employee.
I’ve always had a strong entrepreneurial mindset. I enjoy solving problems, building systems, leading teams, and creating value. The only real limitation is that I don’t have a large amount of startup capital yet.
I’m not looking for a “get rich quick” idea or validation for something I already have in mind.
I’m looking for mentorship-style advice from people with more experience.
If you were in my position today, what kind of business would you start building over the next 5–10 years?
Not necessarily a business to launch tomorrow, but one worth positioning yourself for.
What industries or opportunities do you think are underrated right now?
What skills would you invest in?
If you could go back to 28, what would you do differently?
I’d really appreciate honest advice—especially from people who went from a well-paying corporate career to building a successful business.