These articles show the risks of hiring unlicensed contractors to do your HVAC work. You can save a little money up front but if something goes wrong will you be able to find the person responsible? Will they be able to perform warranty work? What happens if they get injured on your property and do not have valid insurance? 

• www.achrnews.com/articles/126495-the-dangers-of-unlicensed-hvac-contracting
• consumered.georgia.gov/ask-ed/2016-07-18/using-unlicensed-hvac-contractor-can-void-your-warranty
• ​www.achrnews.com/articles/119837-unlicensed-activity-threatens-credible-contractors
• ​altempmech.com/blog/5-red-flags-of-an-unlicensed-hvac-contractor/