As employees, we don’t often think of the cost of our employment to our employers. If you are referring to a paid vacation, there is the expense of paying your wages while you are away, in addition to your replacement’s wages.
Vacation allotments and when you are eligible, are topics that should have been discussed on your hire.
It might be wiser of you to raise the topic of vacations with your employer. You may find that they are generous and willing to help you out.
Conversely, you may find that they don’t have a vacation policy, so you won’t be getting any.
Once you know the company’s policy then you can decide whether to ask or not.
An alternative to asking for a week’s vacation with such short employment history with the company might be to ask for an unpaid leave. This doesn’t provide you with wages, however it only costs your employer the wages for your replacement. They end up paying the same amount so assuming they readily have someone to replace you while you are absent.
Its something to think about. It might work for you. It depends on how bad you want the week off.
As originally answered on Quora.com