EPA card
 

Have I mentioned that I am the proud holder of a brand new , shiny EPA card . It is the first level . As I remember it , the EPA recognizes me to work on small appliances with up to 5 pounds of refrigerant . ( May be up to & including 5 pounds ? )

No , I am not going into HVAC as a business . Just plan to work on my own stuff .

God bless
Wyr

You actually don't need it if you're only working with HFCs.
Technicians and Contractors Frequently Asked Questions | Ozone Layer Protection - Regulatory Programs | US EPA
I'll most likely get mine once time allows (local test center schedules conflict with work) so I will have the flexibility to reuse parts out of old R22 equipment and repair such equipment. An EPA certificate would definitely help you when you're buying parts from the local suppliers, but it turns out that it's generally much cheaper to just buy parts online.

If you're building your own stuff, it makes little sense to use R22 unless you recovered it from equipment you recycled.