I don't post a lot in this area because questions like this irritate me. Jumping in with the sharks then asking the boat captain if this was a good idea, and if he could throw you a life jacket, oh and some shark repellant.
But we've all got to start somewhere, right? So I'll share with you some of my experience in this industry.
First off, if you think you are a designer, your feelings will get hurt. Secondly, really good designers rarely make good businessmen. Thirdly, have some design principles and stick by them. That's the only way to be able to stand out in a crowded field, is to have good design, and a no-compromise attitude. (But there's the double edge sword, because that's not good business sense all the time. Sometimes you have to take it up the arse to be able to pay the bills) Then when you've thoroughly compromised your design principles, and put 5000 yard signs with Helvetica Black, because the client didn't share your vision for visual eye candy design, your feelings will get hurt.
OK, here's how it all got started... I worked so many different design jobs over the years, learning everything I could along the way. From Print Shops, Newspapers, Fancy White Shirt Design Studios etc... Hung out at a friend's garage based sign shop. Weeded vinyl while chit-chatting. Watched his business grow, and I even helped out in my spare time. He didn't have a printer, but just a plotter. Prints were outsourced, and almost rarely needed, because that wasn't his focus. Eventually, I thought I wanted a plotter... so I talked my boss into getting one, to add to the business offerings. (I was working at a mom & pop print shop at the time) So, I learned how to do everything on their dime, using their materials. Then I got good, and we were making good money. Sometimes more than the print shop part was making. Which allowed me to broker them a deal with one of their suppliers, about getting a printer. Wasn't a solvent printer, but just a really good wide format for indoor posters and prints etc. I subsequently struck a deal with one of their clients, that if we had this capability, would you be willing to buy your posters from us? Again, I never used any of my money, but was gaining valuable experience. In both the equipment side, and the customer service side and the owners were impressed.
Eventually, I got to the point where I knew I could do pretty much the same thing on my own. And once you get that in your head, look out... you can never work for someone else again. I knew what I wanted, and what equipment to buy first. I knew what I wanted to target, which was everything. (Bad Idea) Either just do trade show exhibition graphics, or just do car wraps or just do signs and store fronts. etc... pick a focus. Because if you've never wrapped a car, you will suck, and the job will suck, and it's not as profitable as it used to be. Plus you need to have good insurance in your shop space to house a car, especially if it might be overnight. Plus, wraps are practically commodity throw-away paint skin now. So if you want to do Events and Trade Shows... don't even bother with that toy printer Roland 540. Waaaay too small and slow to do the big jobs. Plus the ink alone will eat your profits. You need at least a 10 ft wide printer to enter that market. Where you buy bulk ink by the gallon, and it's really cheap then. Also, you'd need a router to do some of the POP work that those shops can crank out along with all the other associated media that is usually required at a Trade Show. Many vendors will likely pick the one printer that can handle all the needs and get the colors right.
Oh, and don't get me started on color consistency! Oh, man... that was so hard when I first started out. Mainly, because I was just starting out I couldn't afford real RIP software. Which is about $3500 for a decent one, and you'll need to figure out how to use a color calibrator. And those aren't cheap either. Matching client colors is paramount. Sometimes you can lose a client if you can't be consistent, month to month, year to year. It's happened to me. And all because I switched to a cheaper ink, because OEM ink was kicking my arse.
See my point is, I got hands on experience with other people's money and machines. And I when I finally branched out on my own, even hard a hard time. Because it was a battle between hitting the streets and passing out my flyers and business cards and going to the social business mixers to drum up new business. But that left me no time to be in the shop designing. Which was my real passion. Then I found I couldn't do the work and drum up business at the same time. God forbid if I had a stuck nozzle, or ran out of ink over the weekend. Try and get a salesperson who will only work on commission... haha! They aren't very good at sales if they take you up on that offer. Even if you offer to pay them 50% profit, just to get anybody to do your sales... they are lazy and don't know your product like you do, and don't share the same passion for what good design can actually do for a business.
So you wanna know what I do now... I'm back to being just a design studio... that happens to have a large format printer, plotter, router, large laser, printing and bindery machines etc... and they are all paid for cash. I only work on the jobs I want to work on, and ones that might utilize some of my equipment. If it happens to be a large sign job, I can do that. If it's just branding and they don't want anything else, well that's OK too. I have a package for them as well. But I name my price, and they can take it or leave it. I even offer retainer options for the more budget minded businesses. I did one wrap last year, only because I happen to have the space, and it was just a food truck, so it was easy. But I wasn't cheap... and they knew that coming in. I wanted to make sure it was worth my while. But they wanted my design, so the cost wasn't a factor. (I wasn't going let my design go out the door to a competing shop, unless they bought out the rights for it) But see, since I had the ability to keep it in house, I made money on both sides of the transaction. But I don't seek out the large trade show jobs anymore. Because just making money isn't important to me anymore. My free time is priceless, and I love being able to come in at 10 or 11, crank out some work and just leave and go and do whatever. Yeah, it's cool making 40k on one job... but you've got to work like you are earning 40k in a week! Then pay all that back in payroll, and taxes and materials... and you end up with only $5k in your pocket. Whereas, with my method now, I can make $5k just with a branding package and never have to turn on a single machine. But it's there when I need it.
Think real hard about how you want to do this sign business thing... because unless you've got a gift with a paint brush, it's really only the business to be in, if you are good at business. Design takes a back seat to sales, commitment to the client, seeing the work through and making deadlines at all costs.
I'd seriously work at a sign shop as an apprentice first. There are so many subtle nuances that can make the learning curve a cliff of insanity, especially if you don't have the experience to navigate the work-arounds.