Thanks @Mike9241 Mike, really appreciated your clear example.
Now I got the cost basis when calculation the rental basis: always LESSER one, as also pointed out by other experts of @AmeliesUncle and @Carl (thank you both too!)
follow-up question on that recapture: based on your listed example, for that 70k "gain not qualifying for home sale exclusion": we will have to include this 70k gain as the "investment income" into 1040 and pay the ordinary income tax for the sale year?
