I returned to school after 12 years in engineering. My wife works full-time, and I have 3 children. After discussing my undergrad grades with the [local] med school, I decided to quit work and go back to school full-time. I did 11 hours during summer, 15 hours during Fall, and 7 hours during Spring - all life science and chem. I also put in 300+ hours for the Spring MCAT, including reviewing/relearning Physics and GenChem, as well as giving myself a crash course in A&P (which turned out to be unnecesary). I held two volunteer positions, and also stayed on top of my home remodeling projects. I saw quite a few 70+ hour study weeks, and the typical study week was 60 hours. Honestly, it wasn't that bad. Of course, once you've been an engineer for a few years, 70 hours on school is a piece of cake.
But, let's put all that in perspective. My family didn't fall apart - in fact, we may even be stronger. My kids are doing fine, and their school grades are top notch. My wife ended up getting her dream role at the hospital, and got her opportunity to kick off some new nursing programs. The money has worked out, and my health is fine. My post-bacc GPA was 4.0 with A+'s where offered. I had the highest grades in class (usually by 5+ numeric points), except for Organic where one person beat me by 1 point each semester. I scored 30 on the MCAT, which isn't great, but it's good enough considering the "brain fog" present. In retrospect, I think that I could've tackled a 21 hour/semester equivalent and still kept a 4.0.
Anyway, the point of all this is not paint everything rosey, or to say that this will get you into med school. It is simply to say that you can accomplish some big tasks if you have the drive and commitment. My drive came from an experience reflecting what Danny Thomas once said: "No child should die in the dawn of life". Anyway, if you have the drive, go for it ... take the pain ... and have fun.