there are also middle way
lev 4 trainer is not soo expensive and not so bad compared to lev 5 trainer
but make money with training is not so easy now, high potential trainee use to cost really much (if they have not orrible starting skills) and is hard make big profit if you pay them much, low potential cost not much but for make money on low potential players you most train them in particular way, SF-PF or PG/SG with interesting IS/ID... if you train low potential players in traditional way is hard sell them at high price.
I thought I would try upgrading my lvl 4 to a lvl5...but doesn't seem feasible these days
if you look at my US team, I love training Star and AllStar level players...for my own team and then selling between ages 28 and 32...serviceable starters and great bench players