Transfers are just printed off of regular printers?

Do you mean ink jet transfers or plastisol transfers?

ink jet we think, she used transfer express (goof proof transfers).

Those are plastisol transfers they sell. I will be using them also. Good companies to look for ready made and custom product are Transfer Express (great for school and teams and product from their idea book)
First Editon (great for low minimums, low cost and custom design work)
Impulse Transfer
http://www.impulsewear.com
Thousands of ready made designs. really great stuff here. Lots of sizes and categories.

Thank you for your response.

So, is it more economical to go that way? I know they have quite a few designs to choose from and the price was reasonable. However, we were just curious if it would be less expensive to do this on our own.

What would be the best way to go when a customer would like a photo printed on a shirt with text?

I use iron All/ Miracool transfers for this. I work with local prtrait photographer and he sells the photo shirts and I do his work. I think if your talking about simi large orders for lets say a business and you want great results then I would go with custom transfers from first edition as long as it doesn't have a lot of colors.
If you have someone who wants a few tees then you may want to go with doing it yourself. An example is the bowling shirts I am making for my photographer friend for the bowling team he is sponsering (see Videos on how I do them)