As a person who has gone through the post collegiate process and has seen many other runners do the same, I believe I can give some insight. Most runners continue to run for a year or so after college, because that is what they are used to and it is their routine. But, soon after they realize they don't have the team structure or anybody there to help them keep training. They also probably have a job (full time) and or family that prevents them from training to their potential. Soon, their competiive running will end.
Others, who really love running, have a plan to compete and continue for a few years. They have hopes and dreams of setting PRs and making US teams. They think that the only way to do this is to get a slack job and train as much as possible, putting off their professional work goals in the mean time. This, is generally the best way to get good in the short term, total dedication to running. But, I think this can only go on for a few years, unless you are a real stud who gets paid to run, as most people want cars, TVs, rent paid, food, etc and the american way of life. It is also hard on relationships, girlfriends don't understand running like you do and they want to do to dinner and movies and get presents weekly. I think, it is important for runners to see the big picture. YOu can run and work at the same time. If anything, work part time at a job that is giving you real experience for a career you might want to do later. It looks much more impressive to work part time for a law firm than at the local shoe store if you want to get a real job. Look at rod dehaven, he was working 30 hours a week(usually 40, but they let him cut back for the olympic trials), he also has a family, and he won the olympic trials, beating many "full time" runners with no jobs. so, it can be done, and done effectively. Also, if we use Wejo as an example, he is continuing this website, which i'm sure is a full time job as he trains. He may not be going to the old 9-5 job, but it is work non the less.
so, in summary, I think that if you want to continue to run and for many years after college, realize that eventually you should find work that suits your training and allows for growth in some profession other than running. You can have both!