Most all of the information you need is in the post by @Chris Mason . One more piece of thought:
Just because you can buy a house (1-4 units) for $0 down, doesn't necessarily mean you should. The numbers still have to work. My VA-purchased 4-plex still hit all the magical rules of thumb, as well as checking out in reality upon further analysis. It was a really good investment at the time, and has proven to be the best one I've made. But that was irrespective of it being a VA-purchased property.
In my opinion, it's actually more important that you build in a buffer because you will be fully leveraged. A tank in the market and all of a sudden you're significantly under water in your mortgage.
I can't comment on the difference between using a VA and FHA loan, aside from the commonly known information. I've seen some arguments to use the FHA loan first, since your VA benefit is a set amount, regardless of how many houses you have. (I think the point was to wait to use the VA loan until you absolutely need it)