1) How old is he? What is your training been/going to be?
2) Look on the TL using some of his parameters to find guys of similar skill and see what they are going for. You may have to say 'better than him, not as good as him' to find a price range.
3) see answer #1 above :)
4) At your level (same as mine) I think it is plausible to achieve both. Training=both money and improved play. For me my strategy starts with training, and expands from there. I also managed to scout alot ($) and increase my stadium. I did not, however manage to buy a big time player (level appropriate, of course). My training regime did turn some avg players into MVP candidates (again, lvl IV) which helped my get the #1 seed. For me, training is where it starts.
5) In my brief experience, it seems to be a buyers market early in the season, and a sellers market later. Just my observation.
There are many others here who know much more than I, but I thought I would respond as we are both in USA IV, and experience the same kinds of obstacles. Different ones in the upper levels I think.