“Hey Rich, what kind of guitar should I get my 6-8 year old to start on.”
There are several options. But honestly you will want to spend a little money on a quality instrument, one that is going to make it enjoyable for your child to play. “but Rich I will buy him/her a good instrument if and when they continue playing.” Wrong! If you purchase an instrument that is hard to play and wont stay in tune, they wont enjoy it and may never get to the “continue playing” point. May I suggest the Baby Taylor and Martin small to mid sized guitars. Not only will your child love this type of guitar but in the long run, these are quality instruments that will last. To many times have I had young students show up to lessons with an instrument that will not stay in tune and with the strings so high off the fret board that even I have a hard time playing it. So do yourself a favor spend a little extra for yourself or your child and buy a quality instrument.
“Rich, should my child begin learning the guitar on the electric or acoustic guitar?”
That is really a personal choice. You need to consider that with the electric guitar, it needs to be plugged into an amp and is generally louder. With the electric you also will have to purchase a chord to plug into the amp. The acoustic guitar is quieter, and your student will be learning more acoustic based music if they come to lessons with an acoustic guitar. With the electric guitar your student will be learning more styles like blues, country, rock, jazz etc.. I should also say that some electric guitars are easier to play, but again either route you take, make sure you get something quality.
“How long will it take to get to a level where I am playing songs, and making it look easy?”
That is entirely up to you. If I can say something and then say it again. Practice Practice Practice Practice! Did I say practice? To get to the level where you are making the guitar look easy to play, it takes…. well… practice, repetition etc. Some are born with that little extra talent and make progress quickly, but I have not seen anybody, who puts in the time, make great progress and have seen their enjoyment of the guitar increase with the work they put into it.