This article is from the Radio Control (R/C) Flying FAQ, by Shamim Mohamed firstname.lastname@example.org with numerous contributions by others.
Even though "wet" power is called "gas", it's not the same as car
gasoline. Model fuel is usually a mixture of a lubricant (synthetic or
castor oil), methanol and nitromethane. The power plants are usually
called engines, as opposed to electrics, which use motors (see below).
Engines are available in 2-stroke (louder, cheaper, and more powerful
for the same displacement) and 4-stroke (a more scale sound, less
vibration, but more expensive). Engine displacements are usually
measured in cu. in. the US (A 60 engine = 10cc [actually 0.61 cu. in.]).
Compared to beginner's gliders, powered trainers are more difficult to
master. This means that everything about instructors and equipment
checks goes DOUBLE for powered planes. There are many, many ways a
beginner can make mistakes and destroy a model that he/she has spent
alot of time and money on. With the typical powered trainer, going it
alone is foolhardy and will likely end with a destroyed model and a
very disappointed modeler.
If you can't find an expert that is willing to teach you, it is best to
start with a 2-3 channel model with a long wingspan and alot of
dihedral. The ideal thing to start with here would be a 2 channel
glider. If you must start with a powered plane, a Sig Kadet is one of
the more docile trainers.
If you have an instructor, but have not flown R/C before, you can start
with something a bit more advanced. In general, the larger the plane,
the easier it is to see and to fly; but at the same time, the more
expensive it is. The most popular size is the so-called "40-size" plane,
with about a 50" wingspan and .40 cu. in. engine. The Great Planes
PT-20/40/60 series are good. You can build these with ailerons, but due
to their large dihedral, they can also be flown without ailerons. It
won't hurt to have them built-in. Even though they will not be very
effective, they will get you used to using them. Other recommended
planes are the Midwest Aerostar and the Goldberg Eagle. Something with
a "tricycle" undercarriage, that is one with a nosewheel and two main
wheels, is the easiest to learn on.
If you have an instructor, and have flown R/C gliders, you might want
to start with something still more advanced, say a Great Planes Trainer
20/40/60 or the like. These have a fully symmetrical airfoil and less
dihedral. They are capable of more in the way of aerobatics, but are
trickier to fly due to higher speed and less stability.