I don't know about the legal issues, but there are other options that probably wouldn't have any legal issues, such as MS Sans Serif (originally known as "Helv"), which has been included in Windows since version 1. As its original name implies, it is a close knockoff of Helvetica. I've attached an image comparing the two fonts; Helvetica is in red, MS Sans Serif is in blue. The biggest difference is the uppercase "R" (I like Helvetica's "R" better). The ubiquitous Arial is another option, and it is also a knockoff of Helvetica (though a looser knockoff than MS Sans Serif), and kind of ugly.
There are exact clones too, such as Swiss 721, but if you're going to buy one of those, you might as well buy Helvetica. Keep in mind that even if you buy a font, you still need to read the EULA to find out if you can put it on a shirt and sell it.
There are exact clones too, such as Swiss 721, but if you're going to buy one of those, you might as well buy Helvetica. Keep in mind that even if you buy a font, you still need to read the EULA to find out if you can put it on a shirt and sell it.
