73 is not too old to learn something new.
I am 20 years younger and bought a second hand HQ16 4 years ago. And it sat in my basement for 4 years, until I was able to take lessons in person. I am someone who learns by seeing, doing and questioning. YouTube videos are all well and good, but having direct feed back from an instructor is the best way for me.
So this spring I packed up my car and drove from BC to Missouri and I did three wonderful days of LA workshops with Angela Walters. Now I am not saying you need to do what I did, but I am so glad that I have the time and money to be able to go there. She is a phenomenal instructor.
Why an HQ you may ask? I live on Vancouver Island. Second hand longarms are very rare. Additionally there are 2 HQ dealers on the Island, so I know I have service, support and supplies available to me.
This likely will not be my last long arm, but it is a great beginner machine for me. I highly doubt I would use a computer guided system. That's when you get into the big bucks.
If you go the second hand route, you will find some incredible deals in all the brands.
Check out this Facebook group to get an idea of what is available.
https://www.facebook.com/groups/Longarms4sale/