so that u can re-invest it in other property or do u have to report it that year? thanks

Okay, so here is the situation: My father owns about 16 acres of land. My grandparent’s gave this to him because they were right-wing radicals who believed that paying property taxes violated their constitutional rights, and so they didn’t pay taxes and almost lost the entire land to the IRS! My father paid the taxes and saved the land, and they signed it over to him, with the provision that they have a ‘life time estate’, meaning they both have the right to live on that land. Fast forward twenty years later: My grandparents divorced and both moved off the property. They divorced mainly so my grandmother could get her previous husband’s social security, which was higher. My grandfather was diagnosed with alzheimers and eventually dies. My grandmother can’t live on the property by herself but doesnt want us to sell it either because of memories. He’s selling it anyway behind her back and not letting her know. Is this wrong?! She’s suicidally depressed and wants to cling to the past!
It should be noted that my grandmother has been obsessed with my grandfather (or I should say step-grandfather since he’s not my grandfather by blood), and they actually had a horrible marriage which was actually abusive! But now she’s acting like it was wonderful and she wants to pretend that she can live out there again. She thinks the banks are going to go under and that we’ll need to flee to the country! A lawyer told us that since she’s divorced and can’t live out there, the lifetime estate is voided, so legally he CAN sell it. The problem is, would it be wrong to do so?! She’s very unreasonable about this and tends to scream and throw a fit when you try to even discuss it with her!

I currently have 2 single family homes which I have been renting (and reporting as such to the IRS) for the last 8 years. I understand the gain from the sale is counted as regular income and I hear that I must also add back the depreciation amts. claimed. Are all depreciation $ from past years counted as regular income as well? Is the gain computed from the amt the home was worth at the time it was put into rental service or the amount paid for the home (since I lived in it for 4 years prior to renting out)?
Is there any way to lower the tax burden since it will not be a like kind transaction, although the funds will be used to buy a vacation home which could possibly be rented out in off season?