I know there are alternative surfaces that should work with both Canon and Epson printers, including Canvas, cloth, etc. No certain about vinyl, though.
For your market, what do your suppliers have the best access to for paper, ink and service?
As to print quality, once the print is on the wall, it would be hard to say that one image was printed with an Epson, another with a Canon. There would be variations between two prints, even with custom profiles, but each would be aesthetics, not absolute image quality.
I purchased my last printer, an Epson 9800 second-hand from a photographer moving on the Canon. He liked having new printers with service contracts but had used it once just before sale to update a few odds and ends on this printer. The printer before this was a used Epson 7600. No problems that a simple head cleaning wouldn't fix or replacement of a maintenance tank or cutting blade wouldn't fix by myself.
I've had the 9800 for three years and and 7600 for five and like you plan, I've done outside printing for select clients.
I purchased the 9800 to go larger (44 inches) and to do canvas. Both printers have paid their way through the years and I use them for my own work. If you can get your hands on a newer used printer, I don't think you'd have too many problems and could save money on the hardware.
Basically, I can give you "Kentucky windage" on the cost per square foot (multiply these by 10.76 to get square meters). Predominately, I use Epson Luster and Epson Matt paper, 24 inches, and 44 inch Fredrix canvas.
The paper is easy, Luster is generally about $100 to $110 for 100 feet, 24 inches, or 200 sf. That puts the price roughly at $0.50 per square foot. Canvas runs about $133 sf. Ink consumption on the 9800 is a maximum of 2 cc/sf, about another $1 roughly per sf. Not including supplies, maintenance, cleaning cycles, etc., consumables run roughly $1.50 per sf or about $16.15 per square meter where I live in California. I figure I need to double this to get my base expense when I'm printing hot and heavy, or about $3.00 sf on Luster, $32.30 sq. meter, just to keep the printer going. Included in my costs are the shipping of the materials. Paper at $0.50 per sf sounds great, but if you are paying $30 shipping to get it to you, that adds up quickly and pushes up the price drastically! For ink, I use the largest cartridges I can which will give you the lowest cost per cc of ink.
But at $3.00 sf, I'd go broke quickly. I still have to factor my computers, software, training, knowledge, electricity, building, rent, retirement, replacement, continuing education, etc., etc. Thus, I charge about $12-$15 per sf for paper, and double that for canvas, which I need to charge even more for the coatings I apply in addition to the extra handling and maintenance I've got to do.
What you need to do is find out what it will cost you to purchase the ink and ship it to you along with the paper.
For the printer, new, these things are quite large and come on a crate which if you have a loading dock, no problem to have unloaded. If you don't have a dock, you'll need a truck with a lift gate. That will cost more as will the freight, depending upon where you live. That much more to consider.
Have you checked Craigs List and eBay for used printers? There may be something within a short drive that you could purchase second-hand in good working order from someone either up- or down-grading that would work just fine.
If you do, you'll need a pick-up or enough room on the 9800 size printers of at least 2 meters and about 150 KG capacity. You'll also need at least a couple of friends with strong backs to help you set up your new printer and if you have stairs, like me, they've better be pretty burly to move it without dropping it!
HTH and good luck with your new endeavors!