Welcome to E-biking.
I don't think you'll find an ebike that is only electric (unless it's a scooter or motorcycle). All e-bikes are pedal-capable.
Having rear wheel gives much better traction in loose soil, wet surfaces, etc. because your weight is on the back.
However, installing, maintaining, and such is much easier on a front hub. If you spend most of your time on the streets, then front hub is fine.
Lead acid is great, but heavy and space-consuming. But they are cheap.
Pingbattery.com is where you can get great batteries at good prices (LifePo), but they cost about two to three times the cost of sealed lead acid.
Try ebikekit.com. I've ordered two kits from them (talk to Jason) and they are (in my opinion) the best. Why?
1. They sell a complete package (whether you get a battery from them is your choice). You can order from them and get 100% of what you need in one simple package.
2. They are put together in the USA.
The Chinese are fine people, but everytime you spend money with an American company you help the U.S. economy.
If your budget is about 500. Get the Ebike Kit SLA kit. If you have 700-900, get the EbikeKit and order a battery from Pingbattery.
You need to tell us how far you want to go and how fast. Those two questions are important.