Re: Which engine for a beginner??
Welcome to the club! Lots of helpful and knowledgable people here.
I ride FD exclusively, and built my bikes for free. I had many of my materials laying around the garage already. Using little more than old chainsaw engines, bike peg drive rollers, and brackets (are different for every mount; requiring some fabrication skills). Many other things can be used as engines for your project, for example: A weed whacker, leaf blower, chainsaw, etc. can be found easily and at a reasonable price in my area. Not sure about AZ, of course.
The DIY section has all kinds of things like this. My build threads are fairly thorough, and may be of some assistance if you decide to go that route. Keep us up to speed on the developments!