I think the number 1 requirement is that you be a moron. My last trip across the Atlantic I talked to a guy on the radio that was at 12,000 feet going across the Atlantic in a single engine Cessna!!! And to top it all off the goober was bragging about it! "I have a brand new 206(I think) here - avionics are great blah blah blah". Brand new airplane, which is when the chances of engine and systems failures are at the greatest, with one engine doesn't leave you a whole lot of options. The pcuker factors going across the pond with 2 jet engines is sufficiently high that I can't imagine why anyone would do it in a single. I don't know why manufacturers don't just pull the wings off, ship it via ship, and bolt the wings on over there. I guess it's cheaper and faster to find someone that enjoys putting themselves in a high risk situatino and let them fly it. Don't be that kind of ferry pilot.
Being a ferry pilot to deliver airplanes that had been sold domestically would be an interesting job I think. I don't think there are any particular requirements other than the basic commercial,etc etc....Insurance company may require 25 hours in type or something like that. If the airplane requires a type rating you'd need to have that. Interestingly enough the FAA can authorize you to fly an airplane that requires a type rating without having one but it's very rare that they do that.
If you're interested in doing something like this I would recommend just calling aircraft brokers and maint/mod. shops in your area and let them know you're available.
I've thought about ferry flying (domestic) but I'm leaning against it ... and so are most brokers & insurance carriers.
It all comes down to familiarity with the individual aircraft and more specifically the systems on that aircraft.
In a strange airplane, if something goes bad, you just don't know where, what, when those specific systems will do, or not do.
There are countless stories of relatively higher time pilots getting into an airplane for the first time to take it someplace and they end up dead. And, it precisely those stories that have my local FBO requiring that if you want them to sell your aircraft you deliver it. They will not send a pilot to get it or deliver one they've sold.
Doesn't mean it can't be done, or done safely, but it's just an added risk for a relatively low return, IMHO.