Most national postage services offer a calculator which will let you calculate your postage costs before you send and the sort of packaging that may be required for items along with their costs. Some delivery times vary as there won't be a plane that leaves every day otherwise we would be wasing a lot of fuel in one year for shipping, however usual delivery times for domestic services take around 1-5, a optimum of one day and maximum of 5 working days to arrive.
For international postage the fastest i've experienced is two days from across the world which is amazing however there are occasions where it may take 1-2 weeks and a maximum of 28 days which is rare but possible as stated earlier, there can't be a plane bound for each city every single day.
Of course, one can use an express or private service such as Fed Ex which would garuntee a speedy delivery however costs are listed to go above $15 for the service alone (excluding weight, size).
For more information about postage, you can always google your country's national service,
Australia- Australia Post
United Kingdom- Royal Mail
United States- United Parcel Service