I know this is a bit of a resurection but if Hassans still thinking of this ??...
I do this in my spare time - the main money ( ) is in maintaining and repairing, yep by all means build one, sell one, but its now cheaper to buy a pre-made unit than to buy the components
I live in a rural area and the bulk of my customers are the over 60's, supplying them ink, recovering BSODs, the odd new printer but mainly re-installing MS windows