A gap year is literally a year off from studying, not compulsory but quite common, usually taken between the end of college and the start of university.
So I don't entirely understand question 1, because why would you have to pay to just not study for a year? If you're doing some sort of gap year trip abroad then yes of course there would be costs involved, but many people don't travel in their gap year.
As for question 2, yes it's better to apply now and put the following year as your required start date. That way your place is secured.