To find a base you have to build a signal scanner and choose Habitable Base, then you go claim it and get to building. Freighters are definitely expensive, the latest patch tweaked the prices but I'm not sure how. I looked at one last week and it was 80 million. There are a bunch of ways to make money, farming/trading/scanning flora and fauna(this is actually worth it now with the new scanner upgrades). It's time consuming as hell but I'm basically addicted to it.