Controllable flight can be up to 1 mile in the air. Although your ability to discern it's presentation at that range is extremely difficult if able at all. Most are flown within 500 feet of the pilot.
While this depends on the fuel tank size, most have enough fuel for a 10-15 minute flight time on standard sport plane. Most flying is done in a 10-15 minute range to give the pilot a break, and allow others to share in the fun.
This also depends on the airplane. As some small ones start around $200.00, to the sky is the limit. However, the standard .40 size trainer goes from $350.00 and up with radio and engine. The engine and radio can be transferred to other similar sized models if the pilot decides he wants a little variety or is ready to move up to a higher performance model
Almost Ready-to-Fly are now constructed as well as kits. But with an ARF the builder gets into the air quicker for the same cost, or less, as buying a kit and all the items needed to complete the kit. Also there is less "emotional" time invested in an ARF as a kit will take a longer time to build. Presently, this is the most popular way to go as we all find less time in our lives to do everything we want.
Absolutely NOT. If you preferred to construct your own, this is also a rewarding part of this hobby. Kits are not hard. Modern sports kits are basically a jig saw puzzles that have instruction where to put the pieces. And you assemble those pieces with instant glues.
Your first should be a trainer. This size should be .40 cubic inch displacement engine size or larger. And almost anything with a high mounted, flat bottom wing works well. You can purchase these models at your local hobby shop or a on-line retailers.
There is no fixed time line. Some learn faster than others. But club instructors will adapt to get you soloed as quick as you are capable while still being SAFE. It mostly depends on how much time you can devote to the initial training process. It's very similar to riding a bicycle. Once you learn it you never forget it but practice is of utmost importance during the start and the only way to do this is by getting the stick time. Computer simulators are available and amazingly realistic. But there is no substitute for the real thing. Simulators can help you learn new maneuvers (safely) and the all important practice especially when the weather is less than ideal.