Ducted fans will be your best bet, for sure. The batteries and electronics will need to lay along the middle of the model to facilitate ease of balance.
Servo's can be had for pretty cheap on Flea-Bay. Articulating the engine pods won't be too difficult, and will likely be easier than trying to set up individual throttle controls to all the engines.
The most important thing to remember is centering your weight. You'll have a much larger area of slop to work with if you use four motors than you would if you only used two, but with two, you could actually make a model fly like an airplane. When figuring your center of gravity, start with the following information:
Desired size/scale of the model: This is the lynch-pin of the whole plan. Size will dictate weight, and weight will increase considerably just by making a model 18" long rather than 12" long.
Size of the motors: The spindle will actually be where your CoG is most accurate. For two motors, the CoG will be a straight line through the two spindles. For three, it will form a "Y". For four, it will form an "X" with the motors being the ends of the arms.
Number of motors: Four will be more stable than two, but will also be heavier and harder to control. Three motors may be a good compromise.
Strength of motors: For two, you obviously want them to be as equal as possible. For four, it will depend upon placement. The two that are going to be bearing the heaviest load will need to be considerably stronger than the other two. In order to figure this, you'll need to get as close as you can to a total weight of components, especially if you plan on the design being able to lift under its own thrust rather than take off like a traditional airplane. If you can provide enough lifting surface in the wings, and figure out how to rotate the motors, you'll be able to reduce throttle if you want, and thus, make a battery last longer, saving on total weight.
Center of Gravity (weight and balance) is where you will either succeed or fail to make a VTOL function. With two motors, the CoG needs to be as exactly in line with the spindles as possible. Anything else will induce control difficulty. You begin to get better tolerance to this concern by adding a third or fourth motor. For a third motor, you'll want your model to be just a bit tail heavy, so that the load is distributed as evenly as possible amongst the fans. A little slop forward or aft is more easily dealt with like this. However, you still need to be bang on with your balance from side to side. With four motors, you'll gain the most in stability, and your equipment mounting locations within the model will be less critical.
Get a scale that measures as small a weight as possible, as even tenths of an ounce can be an issue depending on where the excess weight is. That brings up the next bit. Once you have determined where your CoG is going to be, you must do the math to balance every item you install into the model. The point of this exercise to keep your CoG as close to the desired location as possible; it will drift as you add or remove components.
The formula is pretty simple. You need the weight of the item and the distance from the desired CoG or arm. (I would recommend ounces and centimeters for this.)
You multiply the weight in ounces by the arm (distance from CoG) to get your "balance moment". Loosely, this means that if you add a 2 ounce weight 10 centimeters from your desired CoG, you will have a realized weight of 20 ounces that you have to counter on the opposite side of the CoG.
As you can see, there is a huge amount of detail that goes into figuring this sort of thing out. But, the good news is, until you get into the moving parts, the math is simple.
Here's a good reference I found to help you out. If you have any questions, feel free to PM me, and I'll do what I can to assist.
http://www.pilotfriend.com/training/flight_training/wt_bal.htm
