Looking at selling one of my rentals and using proceeds to exchange in to buying a house from my mother that she is currently using as her weekend home.

I'll second what both @Natalie Vane and @Paul Caputo said, with a further note that these two strategies can be combined to great effect.Natalie is correct that if your mother keeps the property until she dies, and leaves it to you in her will or trust, then the tax basis resets to the current market value at the time of her death.

I'm lucky enough where my mother-in-law works for a Real Estate Attorney, so he'd definitely double and triple check for me. 

One approach I am strongly considering is a house with a separate living area, mother in law (MIL) suite, additional dwelling unit (ADU), etc.

When my mother dear saw I had spent $150 on this, she got pretty mad at me for spending money on a scam, forbid me for spending any money on anything similar, and advised me to look up and read reviews of Rich Dad company.

My father is a residential contractor, and my mother was a property manager for years.

I just got out of the military, my mother just passed away recently, and I inherited it. 

Owner left no will so the mother is getting the property and wants to get rid of it.

She offered the information that she was not working to take care of her mother a couple of years ago.

But hey, everyone and their mother is looking for MFH so maybe it would sell to some overly eager investor with money to burn.