You don't HAVE to use distilled water. Like Hoosier (and others) said... it's about mineral content.
I'm in the "I retire an atty after a month of use" camp, so Meh. You can always thin with PG too. I seldom add any water to my DIY.
Cheap distilled water: Boil pot with 1/4 inch of water on stove, put lid on for a minute or two, collect condensation. You usually only need a few drops anyway. Don't boil it dry, of course.
As for cleaning atties... I use hot tap water. I blow it all out (well, 99%) anyway, and usually blow out the first few drops of e-
juice too. The amount of minerals collecting on the coil is minimal... vastly exceeded by any other "stuff" in the juice (read flavoring).