Creative writing -- also it costs almost nothing. Fiction, poems, whatever you want.

Painting, drawing and art -- not terribly expensive to get started, especially colored pencil and water color

Solo outdoor activities like hiking, cycling (road or mountain), frisbee golf, cross country skiing, kayaking, canoeing, beachcombing

Photography -- you can just use your phone or buy a fancy camera. Make prints, hang them around your house.

Playing musical instruments -- pick your favorite, there are instructions on YouTube for everything:

• free (singing, whistling, spoons)
• cheap (harmonica, thumb piano, plastic flute, hand drums)
• medium (guitar, bass, keyboard, drums, many strings and wind instruments, electronic music)
• more expensive (analog and modular synths, piano, the larger string and wind instruments)