Teesside, I'm curious. I have many questions. Are you wishing specifically for a Handi Quilter? Which machine and table (size wise) would you prefer?
What accessories come with this one you're looking at now? Are the sellers offering 'help' as well as classes? Ideally, do you want the computer option? (can an updated version be added later?)
Do you live near Connecticut?
Longarm University is a great place to start a shopping search for a used longarm.
Right now, I see an Avante listed for sale in connecticut...you can compare prices, stitch counts, etc. to the one you are considering.
https://longarmuniversity.com/MachinesForSale.html
This web site will give you an idea of what is available out there all across the US, asking prices of different brands, different configurations, stitch counts, different ages, etc. That all makes it a good starting point in my eyes.