When you leave a job, you have the right to take you medical coverage with you for 18 months.(COBRA)
The catch is that the premiums will increase up t0 102%.
All of which you must pay yourself. Believe it or not this is usually, still less money than taking out a policy with the same coverage on your own.
And if you haveif you keep the cobra preexisting conditions and find a new job within the 18 months the next employer can't deny you coverage on those conditions.