RE: first nitro trainer
My son and I built this trainer from the kit:
This is the Sig Kadet LT-40. It is a 40 sized trainer but a little larger than the average trainer in this class. It comes in a kit version, an ARF version and RTF version which includes engine and radio already installed.
The Kadet is easy to build and very easy to fly. Most important recommendation is to join a club and get their help. Trying to learn to fly by yourself is hard on models and dangerous to your friends.
Wingspan is 70" and wing area 900 square inches. Throttled back, it is like flying a glider around. Any 40-50 sized engine will work great. Ours is powered by a Thunder Tiger 46 Pro. We have over 30 successful flights on it now.