Employment contract question (Prague)

Hi, I was just wondering if there is a mandatory 3 month trial period when you are employed here in the Czech Republic, I have read that there is such a period if employed by a company but was just wanting to know if this applied to a person who is, well, self employed/under contract by someone, i.e., you work for someone but have to pay your own health insurance, tax and so forth.

Many thanks in advance.

Andrew