So I just started my game and am seeing all sorts of wonderful houses I own the manor in Anvil and am wonder if I should just save to buy the big mansion thats like 48000 or buy a few houses then buy the big one at the end. I'm not really sure how much money you can end up with.

This is kinda a spoiler, but if you stick with the game for awhile, you will wind up with PILES of cash, and not much to spend it on. I personally would wait for the big mansion, and buy something smaller instead. This way, you'll have somewhere to put all your stuff & decorate.

There are also plenty of cabins, houses, caves, camps, etc. that you can wind up living in which don't cost a Septim.

Before too long in the game, money is like water - no worries. If this is your first time through the game, you might consider buying all the houses as you can afford them, and note which is your fave to settle in or for furture characters. You might find that your fave house will vary from character to character depending on their nature. A noble but unpretentious paladin might enjoy the house in Cheydinhal, while a dark sneakster may be happy in the modest lodging you can buy in Bravil.

Agreed with Acadian.

It depends on if you roleplay or not but there is copious amounts of gold, later in the game. In fact, my thief, Garrett... Only bought the shack in Imperial City and nice home in Anvil (since he saw it as a steal). Now he has enough gold to buy all the houses, yet I won't. I usually just bribe the beggars so I am in the hundreds again