Low-end competition on places like UpWork is mostly piecework, doing small and very specific jobs at sometimes extremely low rates. I don't compete in that market and I don't advise it.
If you want to freelance remotely I advise lining up clients before you start traveling or living abroad, because it's harder to do that remotely. Unless you like churning your customers or doing piecework, you need to aim for long-term relationships. I focus on small- and medium-size companies that don't have in-house IT/programming staff, they are used to outsourcing already. They often have a backlog of work and a history of bad experience with freelancers, so if you gain their trust and show an interest in their business (not just what tech they happen to use) you can find plenty of work.
If you want to find a startup that's hiring remote staff there are online job boards specifically for that.
The business problems I address in my freelancing is taking over legacy applications (usually web sites, and often not very old or even finished) where the original developers have left. This happens a lot -- small businesses are terrible at putting together requirements and specs, terrible at hiring, and don't usually attract the kind of people who want to get hired at Google and Snapchat. I only need a handful of clients to keep myself flush.
My blog (see my profile) has some more specific articles you may find helpful.