The north shore of Massachusetts would be a good fit, but I’m not sure you can find horse property with trails access there, for under 600K (I could be wrong).
Try Groton, MA, and neighboring towns (though Groton is the nicer community, and the surrounding towns are less affluent). It is more bedroom/former farming communities, but the affluence in Groton might support an artist. Also check out communities in southeastern MA, where proximity to Cape Cod means more tourism/possibly more opportunities to display your art at places on the Cape that get alot of tourist traffic. Look at equinehomes.com for some ideas.
I would also consider the Berkshires. You could certainly find a nice small farm there within your price range. But you’d be three hours from the ocean.
Good luck!
