Ron, with your skills and equipment limitations you really should look at an assembled unit.
Also consider that if you build one from scratch it will have to be trued up and adjusted to run right. Some never run quite right because of alignment errors. You have no warranty or tech service to fall back on. All the places that sell assembled frames have aligned things and tested them to assure it runs correct.
You certainly can find a used 3Phase motor and a Chinese VFD, but they will need to be wired up and the VFD probably will need to be programmed. There have been many threads where new people have gone this route and couldn't get the grinder to run right without lots of work adjusting and learning to program the VFD.
Not pushing you to buy a Reeder, but their quality of craftsmanship is superb. Same for the ebay motor/VFD guy. First rate new product with warranty and KBAC tech service if you ever need it.
The grinder is the heart of a good knife shop. Don't try to save a few dollars on it only to regret it on every knife you make.