If you are a US citizen you get visa free for 90 days each visit. And there is no limit how long you can stay in Taiwan in a calendar year. So you could live six months out of the year on Taiwan.
Without an ARC means you won’t be on the govt health plan. But provided you are not needing major surgery seeing a doc is quite cheap in Taiwan and you could easily afford doing so when needed.
IF you have a college degree and you are from an English speaking country you can teach and thus get an ARC and live on Taiwan on that basis.