Read the thread "How to get started with affordable ebike solutions" especially what DW said, then ask questions. Normally, a rear hub is the best solution if there's no reason not to employ one (IGH, belt drive, very hilly commute etc). IMO start with a steel 26" MTB from Craigslist. You should be able to procure a hub kit and battery for $600., and $300 -$400 more if you go mid-drive