On the average, you should be flying solo after about fifteen or twenty flights, some people take longer. The more flying you can cram into one day, the quicker you'll learn. They can sell you everything. You might also see some used planes for sale there, or in the bargain trader. Most flying fields have a bulletin board with used planes for sale.
People get out of the hobby all the time.
You might be able to buy a plane complete with a flight box and all the accessories for a good price. Like all hobbies, you can spend a lot of money if you want to, but you don't have to. Cheaper, if you buy second hand. ARF kits are more expensive than regular kits, but they're easier to build and get you in the air quicker. Your first engine and radio need not be anything super-expensive or fancy.