Think twice about cut vinyl for that store.. Establish a relationship with a wholesale printer like signs365.com for the first year or so.. You're better off reselling until you get enough experience to purchase the proper output tools that support your customers demand. I'd say that digital print will be far easier for you to market successfully than cut vinyl. You basically resell completed cash and carry product that has little labor involved on your end until you get to the volume that demands in house work. Two day delivery is fine with the clientele in your type of store.
I've supplied firms like yours with wholesale products back in the 80s and 90s. I completely understand your desire and am an expert with this product in your setting. Design labor will kill you if you aren't set up for it, and employee churn will not help the matter.
We used standardized designs, from templates, with a simple ncr order form. Then our end sellers sent those to our shop by fax or email for production. You could do that with almost any wholesale printer. I'd suggest you look at selling business cards and printing as well.
You can add design as you get better at the sales end. In my experience serving Office Depot, mail boxes etc, and storage companies, you can expect $1500 per month gross sales, but that requires some aggressive point of purchase marketing. Best sellers are magnetic signs, banners, and decals, all of which require digital print versus vinyl cutting to be competitive. That's why you need a service bureau.
Get an idea of the prices shops charge.
If you go with cut vinyl, the summa cutters are by far the best investment and they hold a good resale value.
its only a freaking sign!