I recently started sewing heavy materials, 500 and 1000 denier pu coated cordura nylon and heavy webbing. I started with a singer 15-91 that I bought for fairly cheap off of craigslist. I love that little heavy black machine. If you can find one, it should serve pretty well for a basic hem on vinyl.
Having said that, after about 4 projects I found the limitations of my singer and decided to upgrade to an industrial machine. I picked up a tacsew 111-115, which is an updated copy of the singer 111w115 machine and it is very awesome for what I'm doing. Its a walking foot needle feed machine and it will pretty much sew anything i can fit under the foot. And with the knee lift, thats a bit over half inch. Cant say enough good things about this machine. It only does straight stitches in forward and reverse but if you're in need of a heavy lock stitch machine its a great one, and a lot less expensive than a juki. I picked mine up from an ebay seller called sewing gold, and it was about $950 shipped including table, thread stand, light and three quarter horse power servo motor. You can get one with a clutch motor for about $100 less but the servo is a lot more controllable because you can set the speed where you want it. Sewing Gold is run by great people, the guy I have dealt with couldn't have been nicer.
An equivalent machine in a juki or consew is at least 500 dollars more.
But pick up an old singer and give it a try. I'm not getting rid of my 15-91 any time soon, thats for sure.