With $140k alone, no, you can't make enough to live off of, BUT you can get a great head start on a portfolio that will eventually generate enough passive income to sustain you.

Both A and B are multi family apartment buildings.The properties are worth around 1.5-2m.I wish to keep A but sell B; preferably in a tax-deferred manner.A is in an area that has been rezoned and I wish to tear down and rebuild the property as the current building is old and I can get more than 4x the square footage because of the new zoning changes.Is it possible to sell B and use all of the proceeds to fund the development of A in a tax-deferred manner?

It's sustainable but with reducing effectiveness.

But you can deliver the message in a manner that is friendly and informative.

@Henry Uili Apart from the great advice you've received, I would add that taking "debt" off the parent's shoulders in this manner might not be the most prudent idea. 

Luckily, my wife is a nurse with a well-paying job, and with savings could probably sustain with me having no employment for a year. 

I was able to get some valuable insights from this book I read titled, Never Split The Difference , and essentially it teaches you that you have to look for information (in this case it would be from the tenant) that is causing him to act in a difficult manner.

Anyone know of a creative way to lock up  the deal put pay the seller in such a manner that her tax burden is reduced? 

For example, if you are a "consultant" and have "consulting" gigs that are irregular and sporadic and have no consistent business that seems sustainable to an outsider.

You can allocate your proceeds in any manner you want as long as you use them all.