What domain knowledge should I learn?
imp: Baby boomers are starting to retire.  That's a large demographic that isn't good with computers.  Maybe find an industry that caters to them where technology can help.  It doesn't sound like fun to me, but where there's muck there's brass.Also, you may not have to be "passionate" about the domain, but you've got to at least tolerate it since you'll need to spend a lot of time doing it.