Generally a 2nd/vacation home will only require a 10% down payment and the guidelines are similar to a primary residence.
HOWEVER, the property will have to meet a couple simple guidelines to be considered a 2nd/vaca home as opposed to an investment property.
It has to exhibit 2nd/vacation home characteristics. For example, it's located in a know tourist area, on a lake, by a beach etc. Generally it has to be a minimum distance from your primary residence -I've seen lenders require between 25 and 100 miles minimum from your current home. You can't buy mom and dad's house or the neighbor's house down the street and have it be considered a 2nd home or vacation home.
It's ultimately going to depend on the underwriter. As always, your best bet is to consult with a loan officer who can pre-approve you and walk you through the process