I want to use a basic typewriter font for t-shirts to be sold. The font I'm using is "typewriter-serial-regular" that is available in Illustrator. Yet when I go to save it, it says I can't keep the font because of licensing. I know how to get around the output, but don't want to be in trouble for using it later. Any ideas?
Generally you can't legally embed (=include) copyrighted fonts into your artwork files. That's because embedded fonts can be extracted from a file and taken to use without paying for them. There's no problem, if the file is used in a place where the same font is available.
But you can convert your text to curves. In Illustrator you select all your textboxes and choose Type/Create Outlines. After that you have no more text objects. They are now drawings, but still look out the same. Of course, no text editing can be done for them, but that's ok, if your work is ready for printing.
You should think the fonts as software products which hold all the information on how to make visible drawings from typed characters. You can distribute your texts as those drawings (=paper or computer file) but it's illegal to distribute the software.