There are so many personal, professional, and other various benefits to building your own EV, but just make sure you're fully prepared that cost savings is not on the list of benefits before you jump in head first into a conversion.
Now, can you convert an EV for cheaper than I outline below? Of course... But with the amount of time and effort you put into this conversion I would highly recommend just doing it right and ending up with something you're really proud of at the end.
AC Motor: ~$2,500
AC Motor Controller: ~$3,500
A/C Compressor: ~$500 - $750
Battery Charger: ~$1,250 - $2,500
Battery Pack: -$5,000 - $10,000
Cabin Heater: ~$500
CAN Controllers: ~$250 - $1,500
Coolant Pumps: ~$250 - $500
Donor Vehicle: ~$5,000 - $10,000
DC/DC Converter: ~$500 - $1,000
Electrical Enclosures: ~$250
Fabrication Material: ~$500
Home Charging Station: ~$500
HV Contactors: ~$250
J1772 Charge Port: ~$100
Motor/Trans Adapters: ~$1,500 - $2,500
Vacuum Pump: ~$250
Total: ~$24,850 - $39,350
I think its really important to fully understand the above total. If you just want to have an EV and think converting your vehicle would be cheapest way to get this... I hope this helps anyone not looking for a project to realize that this is not the cheap or easy way to get an EV.
That being said, if you're willing to dive into a project and have some spare funds to do it correctly, I would highly recommended starting your own EV conversion. Its incredibly rewarding if you're open with yourself from the beginning on exactly what resources you will need to dedicate to this.