If I recruit a C to play SF, what kind of effects could this have both in his play and in his development? Or is there any negative affect to the player in this situation?

Positions that players are listed at are simply window dressing, they do not impact the player's performance once their ratings are generated.

If he's got the ratings/potential to play there, go for it! Like asher said, the listed positions on the player card are just window dressing now that there are no position penalties...let the ratings determine the kid's position. I've had a listed PF playing SG for me before.

As for his development, that would be determined by his potentials and whatever practice plan you assign.

I had a SF play PG for me two different times, and they were great, because their ratings were more like a PG - fast with good BH and Passing. At D3, Palm Beach Atlantic, my SF Johnny Wilson had:
Ath 50
Speed 67
Reb 39
Def 45
SB 14
LP 59
PE 65
BH 64
P 61
STA 100
FT 35
He could play a number of positions, but one year he played PG because he was the best player I had for PG that year.

i just started a pf at sg in D1 for an entire season because he had adequate speed and ball handling and he could light it up from the perimeter...and he led my team with nearly 20 ppg.

he was the best fit...and like those above said, if he has the right ratings, then thats where he should play.