Leasing:
You get a new car for say 3 years and after that time you have to a) give it back or b) pay a lump and buy it.
if you choose a you done your money, you own nothing, if you choose b) you will be paying over the odds for a 3 year old car. Ie it's value will be a lot less than you end up paying to keep it.
Very little up side to leasing.
Now buying:
you get a new car and it's yours, after 3 years it'll be worth about 30-40% (depending on model etc) of what you paid.
conclusion: Forget it! buy a decent 2 year old car at auction for less than half a new one!