If you are on H1 then once you lose your job you'll be immediately out of status. Now being out of status is not a very big deal, but it does mean you'll need to find a new employer willing to sponsor you as soon as possible. USCIS is generally forgiving if your out of status period is not too long (they might require you to leave and then re-enter the country to get back to status though). Also living out of status is not fun - in addition to loss of income you'll have difficulty with things like renewing driver license or traveling out of country.