Hi Trudy,
Welcome! Always great to hear that someone is excited about our sport!
First suggestion: learn to sail. Find a good program close by and get all the basics down before worrying about solo sailing. It's like someone giving you a formula 1 racing car when you are 16...you need to learn to drive a Dodge first!
As to fitness, well, you don't have to run a mile in 7 minutes, but you do have to have some upper body strength and the like. You'll get a better idea of what you need when you start to sail.
I don't recommend solo sailing until you can completely handle the boat alone, including capsize recovery.
Sheldon
P-18