Hi is I worth me buying a horse ?

If your speed attribute is above 85 then it's not worth having a horse as you'll be faster than any horse. And imagine this. You've found a dungeon swarming with chests filled with gold, along with magical weapons and armor. You get only half of the loot before you're carrying too much. So you go to the nearest store and stuff it all in a crate nearby to pick back up later. You then go back, get the rest of the loot, and return to the crate. The loot is gone! That's what'll happen if you don't have a place to store your items. Because every single container exept for the ones in a house that belongs to you will reset themselves. If you don't have too much gold buy the house in the Imperial City for 3000g and the storage area for about 700g.

Ya it is definetly worth buying a house. I don't know what I would do without my house to store tings in. I wouldn't buy a horse. After getting so far into the Dark Brotherhood, you get a really good horse.

I would get a horse cause there cool, but you get a free one near at the start of the game and if you do the dark brotherhood quests you will eventually get a really cool horse, it's black and has red eyes (also this horse has never died on me)
I would also personally get a house, you can keep you belonging there too. If you want a big house that's fairly cheap (i think it's 5000 coins), has some quests with it and come fully furnished go to Anvil and speak to a man called Velwyn Benirus who can be found staying at The Counts Arms!!!
Hope I helped!!

It depends where you buy the house and what your speed is. If you have a speed lvl of 80+ you don't need a horse and if you can barely hold any items, Get a house.