@JTT,
I am doing this on fading memory, JTT, so please don't take this as truth. Feel free to fact check regarding principal residences.
If I buy a house for $100K and sell it for $200K there is no taxable gain as long as I buy a replacement house for $200K within a certain time frame. And, I can claim a one-time exemption from any gain even if I don't buy another house. So if I bought a house in 1970 for $100K and now I am moving into a nursing home, I am not taxed on the gain on selling for $300K. But you can only elect to do that once.
Interesting discussion. We are still waiting for H2o to comment on the article he cut and pasted regarding how this is related to Obamacare.
It is not my call, but I would suggest that this has little to do with the Repub nomination process. It might belong on another thread.