We make a few hundred canvas images on stretcher frames every year. Below is a summary of how we do it.
A good quality canvas is easier to work with, but customers are usually not interested in the difference, they see a canvas is a canvas. But then most of our customers are homeowners just looking for decoration. We also do a bit of "Put your image on canvas" work.
Firstly we use finger jointed bars that just knock together to make the frame. Several sources supply in 2" increments up to and beyond 84". Longer ones need a centre brace.
All the bars have slots near the corner to insert a tightening peg. These are hammered home with a small tack hammer. We find that it's these pegs that are the only reliable way for us to get a nice tight mounting, not surprising, since the bar manufaturers supply them. We have some finished works that are over 5 years old and don't sag yet. If they do sag, you just tap the pegs a little further in.
The hardest part is stapling the corners. My advice on how to do this is to do what I did and get someone who does dressmaking to show you. The thing to remember is that what seems tedious or difficult at first, becomes automatic after a while. We mount a 16" x 24" to completion, starting with a coated print, in about 25 minutes per person. A practical daily person output is about 12 at that size. Even a 16" x 40" print doesn't take much longer because even that size still only has four corners.
We staple at about 2" intervals along the sides and more at corners. Stapling is carried out with the image upside down on a blanket on a table using an electric staple gun and 10mm staples.
The best look for our customers is a wrap around the sides using either "Genuine Fractals" or Ernst Dinkla's Photoshop actions. We Use a soft reflection edge. Using Genuine Fractals you can work on the wrap part to make it how you like because it is a separate layer when first done.
We use "Soft Strand" hangiing wire, held by screwed small ring-and-plate hangars placed on the inside edge of the frame - this ensures a "close to the wall" result.
We spray coat a day after printing (and allow 0.1" extra when printing for a little shrinkage.) There's only a little shrinkage over two or three days but we see more after a week.
Pricing of course is a bit of guess work until you get a regular turnover. Look at what other busineses charge and ask less. To succeed you need a point of difference which can be price, quality, delivery but for us the primary point is exposure. Once we were seen by a regular flow of potential customers the business grew.
If you have a specific question, I'm happy to answer, hope the above is useful.
Hope this is of use.