The reason for renting from us even though they have a house paid off is because their current primary residence is very large and two stories.

I'd recommend discussing the risks with an attorney and at the very least having a plan in place to deal with the worst issues that could arise with leasing your primary residence short term.Be sure to provide proper notice (probably 1 month in advance of the lease end date, but check your state laws about proper notice) for them to leave and it would be a good idea for you to have a neighbor check to confirm they are moving out in the days prior to your returning.

I'm considering selling my primary residence and am contemplating using them to save almost half on commissions.

You may already know but make sure that your primary lender restricts that. 

My day job is WordPress Website Design (https://simplexstudios.com/) so I am slightly basis but I still, think its the best platform for most businesses as it currently powers 30% of the top sites.LearnDash - Learning Management System for WordPress: Great for courses, education, and more https://www.learndash.com/BBPress - Forums for WordPress: https://bbpress.org/BuddyPress - Add social features to your WordPress site, ie friends, likes, favorites, messaging etc: https://buddypress.org/Hopefully this points you in the right direct and let me know if you have additional questions

There are exemptions under this federal law for homeowners financing their primary residence, those in the business of real estate such as landlords are considered dealers.

I love this real estate platform!

Without a homestead exemption on the property (only available if it is the owner's primary residence) the tax rate will be approximately 2.7% (I looked this up on the Williamson County Assessor's site and it depends on the MUD, Hospital District and School District you fall into) which would be $4,050/year or $337.5/month (this may not get reassessed until next year since it is a new build and this is assuming that you will get a valuation of only the $150k not the appraised value of $168k).

Another note, I have my primary residence with my parents.

It has become one of the primary aspects of my business and I’d be happy to share my thoughts.