I moved to an RL24 from dinghy sailing. In a dinghy if you do something wrong you end up in the water. In a bigger boat if you do something wrong you can break something expensive. I think an RL24 is an ideal compromise between the two.
Lot of dinghy sailing clubs have learn-to-sail classes for very reasonable prices or join an club such as Trailer Sailer Club of Qld and sail with someone else until you get the hang of it - see the Links page on this site for clubs that sail RLs.
The condition of older RL24s vary. Be sure to get someone to check out any boat you are considering to buy. A boat surveyor is the best bet.
I have a 24 and it is good fun. However, it is a very hands on boat and my thought is that I would not have liked to have my first experience sailing in the 24. Consider some time in a heavier boat under some mentoring and then you will have the basic skills to confuse yourself in the 24. Once you have it under control .. let me know your secrets as I'm still trying to get on top of the boat.
A great starter boat, but the best way to start sailing a yacht is to start on someone else's. If you can't do that, try to get someone experienced to sail on your boat. Join a yacht club and seek out someone who used to sail RL24's. They will probably like the opportunity to have another sail on one, and they might be able to help you with the purchase and setup. Good luck.