Yeah; that. If you have a laptop and a design program you bought or pirated (Corel/Adobe) and lost your job or cannot find one, a single Unemployment Check can get you into the "business" for about $3 to $5 hundred bux. An espresso machine, even at the low end, is north of $2 grand, and a latte sells for $3 or so bux. Meanwhile a single sign project can be $80 at the low end, or even pay for the $300 cutter and some app supplies, in one fell swoop. So with few jobs out there for workers, they have to make themselves a job, and indeed, this industry has a super low cost of entry.
Something else, that is both encroaching, but also a hug opportunity in reverse is: Apparel Graphics, T Shirt Bling (rheinstones), which by the way, is an industry about twice the size of sign-making. And all those folks being sold stuff to do T Shirts are told that the cutter that comes with the package can make window decals, signs and banners, too, adding to the competition for a very slowly growing market, currently.
So I'd strongly advise considering that in the inverse: If you're doing signs, you can also do apparel, by adding a cheap heat-press, plus some rheinstones/rheinstone pattern & transfer material, Stahls and other flock and T shirt marking. It's a huge market, so it could easily grow to surpass your dollar volume doing signs.
Just my opinion.