dont even worry about outside secondaries unless you playing princeton
Wow... Not trying to be rude, but that is pretty terrible advice. A PF with decent secondaries is a far better purchase than one without. Especially since his plan is to only train inside skills.
To the OP, if looking for a long term PF trainee I would suggest that you find a player with a nice set of big man skills AND some decent secondaries. OD, Handling and Passing combined with some JS would be ideal imo. Height is a large factor in training speed so taller is better, but great secondaries could make you settle for a bit less height.