A friend of mine told me there is no mandatory contract and the employer can make you work when hé wants, there is no minimum working hours by week so no steady salary ?!

That seems crazy , is this true ?

But even in part time, there should be a contract , you know the salary youll get at the end , you cant be taken by surprise with an employer reducing your working time , at least here

Is it difficult to find a full time job without any dégree ?

There should be a contract.. A zero hour contract..

Or your friend found a job in prostitution..

Even prostitutes have job contracts in the more developed countries. An official Job, even if it's just a weekend job, without a contract is kinda unimaginable where I come from.

Though I wouldn't be surprised if this was actually true for the US.

She lives in Atlanta

depends. If you work at McDonalds, no, no contract. If you are salaried, then yes typically there is a contract.

Ha that sucks, fortunately she found an other job in an hotel, a 30h

There IS a contract. But it has nothing to do whatsoever with and makes no mention of your work hours. It's called 'extending an offer of employment' which you accept or decline that states that they can terminate you at any time for a list of reasons, and that you are legally able to quit at any time for any reason.

In America generally speaking you will know beforehand whether or not you will be working full time or not, which is any work week that is 32+ hours of work. So obviously part time would be anything less than 32 hours per week.

At least, this is how it is in Oregon.... But I'd assume the laws in other states are similar

Edit- and as another prior user mentioned, a job that has a salary actually requires a certain amount of hours per week of the employee which would require a separate contract. These are jobs that are more often than not 40+ hours per week. It's a way to get around paying overtime legally, but salary jobs also pay more overall.