I converted a tv unit into a 3 bay enclosure for around $200 and 4 weekends of work. I reckon I could get $400 for it on gumtree if I sold it. If your in it to make money don't bother. If however its your hobby and a bit of cash on the side every now and then is a bonus then go for it.
[MENTION=39292]MathersD[/MENTION] unless you're retired and/or have a LOT of time to spare it won't be worth it financially. As for design - people whinge about the cost on a good day!
I draft designs and cut lists for members of this and other forums for free when they're keen to get into DIY and not sure where to start. You could consider doing the same or trade for enclosure furnishings/fittings which also works well