I had a fairly successful running career during the 80's while working full time as an engineer. I would say having a family on top of a full-time job and serious training would have been too much. You can have two out of the three.
The key is finding a job that doesn't require a lot of overtime or travel and allows a flexible schedule. I would do up to 8 miles at lunchtime and a second run in the evening. I don't know how feasible that is in this job market, but if you're serious, I would sacrifice salary for a job that allows you to train.