I'm Navy Retired (ITC)
I also hate swimming with fish. I've stood the duty as the sharpshooter and shot a shark off Haiti
I also love the sea, and being my own skipper. The link to my blog is below with my signature line. Feel free to browse, particularly this recent one Journey in Patience: Since you asked...
Now then, can you do it? Yes, on the upper end of your budget if you want a good tight boat that will last for years and provide a moderate amount of comfort.
The Irwin 38 CC I just switched to can be had in the 50k range, but will need some upgrading for another 20-30k. That's just being practical. Solar power, systems upgrades, communications, safety and comfort matter, and none come cheap.
Boat and cruiser literature is out there all over the blog sphere and in print - and everyone talks budgets ad nausea. Here's the real deal, you can get by on very little if you sacrifice, or you can spend all you have. $500 bucks buys a lot of rice and beans, some chicken and some fish - but not a lot of beef and potatoes and microwave hot pockets.
Medical care is another area, you mention you are disabled. I assume you have Tricare or the like. Tricare, like medicare is only available in the U.S. I'm sure you've heard that. It's not true.
Go to the tricare web site and search out the overseas options.
As you get more posts (you'll need 10) feel free to private message me anytime.
See you on the water