What’s the best business you can start with $250k?

I would guess that most businesses in history were started with less than this -- it's a pretty broad question. Can you narrow it down? Are you looking for a lifestyle business? A specific field? Are you open to buying businesses?

Check out feinternational.com

It has online businesses for sale, with a few different business models.

SaaS, Affiliate, Display advertising, drop shipping.

Assuming you're somewhat familiar with one type of business model and an industry, purchasing one might provide the most bang for your buck.

Stock trader, because your risk is only 250k. Other businesses involve even more risk than your principle.