Pretty open question.
But here's my generalized answer!
Most news computers, whether desktop or laptop, typically have enough CPU and RAM for Sims 3. The big stopping point especially for laptops is going to be the video. Most video chipsets in laptops are not designed for this level of gaming.
Stay away from video chipsets from Intel or SiS. You need to stick to Nvidia or ATI. The model numbers get VERY confusing, so I'm not going to go into that here.
It really depends on what your level of expectation of what reasonable or fast is going to be, and what graphics level you want to run Sims3 in, but I'd say in general that any laptop capable of running Sims 3 smoothly is going to cost $1000 or more, on average. Stores always run specials on holidays, so you might can find a good deal this weekend. But that may be above your budget.
My best advice would be to report back with some links to laptops you are thinking about and people here could tell you yes or no. And if you settle on a laptop, do a google search for Sims 3 + whatever video it has, to see if others report success or problems. But if you are an impatient shopper or willing to trust a salesman's word alone, just realize you may be very disappointed.
You may find the notebookcheck website either helpful or confusing.
But, it lists many games including Sims3 and how well they would play on lots of laptop video chipsets, fastest video at the top. Go
here.
