Try to give off trustworthy vibes and pick customers/clients/employers who will trust you.

I'm not going to pretend it always worked for me, but it certainly got easier once I could demonstrate a wealth of experience.

There's a lot of luck, too.

In terms of refactoring, I have an iron rule that I never ask for permission. If I think it needs doing I do it. I don't justify it to product or ask for their opinion. Technical issues and priorities are on a need to know basis and they don't need to know. All the work gets baked into feature work and bugfixes.