There is no problem with you deciding to start your own business after losing your job, but know that a court would treat the situation as though you had found new employment. The same principles outlined earlier would still apply.
If your business takes off fairly quickly, and you are effectively able to replace your previous income (or at least the majority of it), that amount will likely be counted against any money your employer may owe you as a result of your termination. If however your business is unsuccessful, or earns a small fraction of what you were making previously, then it will likely not count against you unless a court finds that your decision is completely unreasonable and that you have failed to mitigate your damages.
