When planning your above ground pool its important to consider the amount of water you will need to fill it and if/when you need to empty it where that water is going to flow.
Every cubic foot of pool space needs 7.5 U.S. gallons of water... a small Easy Set pool say 8 feet diameter with 30 inch high walls is 125 cubic feet of space which is almost ONE THOUSAND gallons of water.
If you are lucky enough to be able to afford a large above ground pool then something like a 33' x 18' - 4.5 feet deep will need 20,000 gallons to fill it.
Obviously if you invest in a large expensive above ground pool you are unlikely to empty it very often but it is important to consider where the water will flow if you ever have to empty it. For example you don't want it flowing towards a basement entrance, flower bed etc. I am sure you have all seen the funny clips of pools bursting on America's Funniest Videos / Youtube; just remember to consider those thousands of gallons of water when locating your pool!