Hi Ali! You buy the number of points you want and then can "spend" them at any resort you choose on the size of unit you want (studio, one bedroom, two bedroom or grand villa) for which ever days you choose each year. At the top of this page, there are
point charts for the current years that will give you an idea how much it "costs" to stay at each one of the resorts during a particular time. One thing to mention is that which ever resort you actually buy your points at, you have from 11 months out until 7 months out to make your reservations there and then at the 7 month window, you can make reservations at the other resorts. This gives you home resort advantage, so if staying at a particular resort during a busy time is important to you, it might be in your best interest to look at going resale to buy at sold out resorts. Currently Saratoga Springs is the only resort Disney is selling, but they sometimes have points available for the other resorts as well.
There are definately handicap access rooms at ALL of the resorts. They have roll in showers, lower beds for easier transfer, lower kitchen areas for cooking, etc. Disney is very good about providing HA at both the parks and hotels for everyone to enjoy.
Keep reading these boards and asking questions. There is a ton to learn about
DVC and this is a great place to start. You can also call Disney and request their sales info and they will send it to you and also answer any questions you have with NO pressure to purchase. Just remember, they are not the only place you can purchase DVC memberships, so be sure you get a good understanding of the resale market as well before you make your final purchasing decisions.
Good luck!