consulting, where consulting is often just freelancing, is pretty inflexible about termination - the rule should be that you make at least 2X your normal monthly wage - but adjust for small times (increase, decrease slightly for longer times).
Generally with a 3 month project I do exactly 2 times my normal monthly wage, if I do a direct negotiation with company 2.5 times.
Generally termination is instantaneous because they are paying lots more for me than if I were a normal employee. But sometimes I have managed to get termination for a week or two, never more than that.
500 is not really a large company, although it is for a startup. In my experience smaller companies tend to be more jerks, because to them the money they are paying for a consultant is just WHOAAA. They want you to be productive day 1 and not mess anything up ever. Really big companies think productive in a couple weeks please, and if you do significantly better than that they are pleased. I like consulting for big companies because I get my money, they like to renew me, they don't care about what they pay they just want to get the results. I hate consulting for small companies, and will pretty much only do it anymore if project really interesting or I have friends there.
on edit: fixed typo.
