This is going to be an expansive purchase so there are few things you need to consider. Number one thing to consider when purchasing the pool is the size. I cannot tell you how many people misjudge the size of the pool. Measure the space two times before deciding the size.
If you are going to use this pool you should get the package set, and not just the pool. The reason is that the above ground pool require the same maintenance to keep it clean as in ground pool. So you need to have the pool pump, cover, the ground cloth, ladder etc. Because if you buy it separately it may cost you more.
You also want to select the one that has a sturdy build to it. Not something that can break easily. Such as ultra frame pools and they are looking great too. If you really want the large lap pool you can go with ellipse or a frame set pool. Since you are spending a lot of money on this, you need the pool that is going to last you a long time.
Just to be on the safe side, make check with your city/town guidelines to make sure you do not need special license or permit to have one of these pools in your backyard. They are large size and contain a lot of gallons of water so they may require you.
The pools can range you anywhere from $60 to couple of thousands of dollars, depending on the size. The cheaper once often do not come with the pump, cover and ladder. It is very important to have those because it will keep the water in your pool clean.
The most important thing to consider when purchasing above ground swimming pool, besides the measure is the fact on how often you are going to use it. If you need it only temporarily and use it once or twice a year, than cheaper is the better choice, but if you need it to last, you are better off getting a more expensive pool.