Hi,
I'm not in your age range and started working on my PhD right out of college, but I just thought I'd throw in some info that might clear things up. I don't know what field you are intending to study, but many PhD programs provide a student stipend. They are usually not large, but depending on where you live, you can usually live frugally but fairly comfortably. This might allay your concerns about loss of income- you will probably be making less than you were at you current job, but at least you would be making something. Also, most of the programs that I'm familiar with include a tuition-free scholarship, so the cost of classes might be almost nothing out of pocket for you. In terms of living away from home during the week, typically humanities programs involve lots of reading and research that can be done at home, with the exception of actually taking coursework, so you may not be stuck on a college campus monday thru friday.
Just to put this in perspective, I'm in a PhD program at University of Notre Dame, in Biological Sciences. I'm in my (gulp!) sixth year. My student stipend is $23k/year, and as part of admission includes a tuition waver of about $30K/year. For science, we take all of our coursework within the first two years, and spend the rest our time doing lab research under an advisor.
Keep in mind that all schools are a little bit different and there are even differences between departments. Arts/Humanities students spend a lot less time on campus once their course requirements are ment.
If you're serious about going back for a doctorate, I would suggest finding a professor that you are interested in doing your work with and contacting them. Professors who see that you are serious and show an interest will be advocates for you when your app is being reviewed by an admissions committee. It's always nice to have an 'in'.
sorry this was a bit long, i just had a similar conversation with a friend who is also contemplating grad school.
good luck!
cristina