So for me (also do IT/Security consulting and repair) I have:
EDIT: Also have two versions (x86 and x64) of AntiX for general purpose stuff. Boots into RAM like puppy but I find it a little more useful.
I have these running on a 128 (I think, might be bigger) flash drive that I actually have looped on my keychain. I have found that 90% of the things I need to do can be done from that, and having it on my keys means I always have it ready. Unless I lose my keys for a while that is…
DBAN is for HDDs and using it for an SSD is not really worth the effort. If the SSD manufacturer does not provide a wiping tool (Samsung does for the EVOs) and you need to make sure the data is wiped, you better crack it open like a clam shell and destroy the board inside. In my opinion you should never sell or give away a used SSD because of that.
Not a problem, I enjoy passing down knowledge even though I am still relatively new in the field as well (5 ish years). Good luck with the business! Don’t get discouraged if it starts slow, don’t be afraid to admit that you don’t know how to do something yet, and never stop learning.