Sup brah, you need to go to legendarymotorsport.net on the in-game internet (it's under travel and tourism), this is where you buy all your best cars from and one of those is the Elegy RH8. You should notice that the Elegy RH8 is free whereas all the others want money as normal, so just select the Elegy RH8 and it will be sent to you. I am not sure if this will work without a garage (the cheapest are like 20,000 in game dollars and can be bought really quickly though).
A word of warning however, the Elegy RH8 cannot at present be removed from your garage! Anything you do to try and remove it will at best do nothing and at worst cause another of your cars to be deleted instead. So consider the fact that this car might forever take up a spot in one of your garages (hopefully this will be patched at some point but Rockstar have not acknowledged the issue even exists yet to the best of my knowledge); the largest garage you can get is 10 cars worth of space.