Rich,
I' ve playing ball for the last 18 years - started indoor at high school and moved to beach for better scenary. Welcome! The most important question you need to answer is what type of fabric(s) do you want to print to? The reason being that
DTG printing is really best done on natural fabrics (i.e. cotton). I remember my days in high school volleyball and I know for sure that the jerseys were not cotton. Plastisol inks do much better on synthetic fabrics.
DTG excels at doing short runs and photographs (i.e. designs with a lot of colors in it).
I agree with Michelle. Think about outsourcing some of the work or even look at plastisol transfers. We had a minimum of 12 guys on our high school teams. Look at a plastisol transfer company that has low minimums. F&M Expressions is a good example. All you need with plastisol transfers is a heat press. If you are looking at going with photos on shirts...your options are really
DTG or Sublimation. Sublimation is the longest lasting decorating technique - but really only works good on polyester shirts. Think about all the warm up oufits (i.e. Under Armor type fabric). Unless you are going after the onsite production work, I would not lean toward
DTG printing based on how you described your business model. More information might change this initial gut reaction
Hope this helps. Feel free to ask more specific questions.
Mark