I always avoid signing an exclusive buyer agreement that goes past the date of closing.

It's tax law, so there are numerous exceptions, restrictions, and extensions on that "section 121 exclusion", but that's the general concept.)Since the property was gifted to you, you have the the gifter's basis in the property.

The downstairs tenant also currently has exclusive access to the 2 car garage. 

According to this website, Citi cards are the best for extending the warranty: https://thepointsguy.com/guide/best-cards-for-extended-warranty/.I read the exclusions on the benefits/disclosures brochure associated with this card, and the only thing I saw that wasn't covered similar to what you're referring to was "Items purchased for resale, professional or commercial use." 

Off market can help you find better, more exclusive deals.

I work exclusively with investors here in Nashville.

For example, if you exclusively use one 10' x 15' bedroom (150 sq ft) for your day trading, and the whole house is 2,000 sq ft, then the percentage is 150/2000 = 7.5%. 

That's an exclusion. 

My mother was told she must sell their home by the end of 2018 to qualify for the married $500K gains exclusion.

@Alex Cervantes it sounds like she might have an agency listing agreement instead of the more typical exclusive right to sell.