My biggest problem is I'd love to detail cars all day. However, realistically the pay doesn't pan out. I make a decent amount at my ready and steady job...but if I was going to go back into the self-employed mode, I can probably get away with charging at most $300 for a full detail. That would take me a full day....perhaps part of a second day. I can do anti-virus installs and general PC work at $100-200/hr.
I get more satisfaction out of the detail work.
Unfortunately much like PC work, you get assholes calling you back about extremely minor details and things you had no control over.