I used to think under 20 WE was about the cutoff for guys not being worth it. Is this still the case with new engine? Would you ever recruit a guy with an 18 WE?               

They won't grow imo because my PG with 23 WE only gained 20 pts last season, and he's high potential in alot of areas. 

If the player is good enough to start by fresh/soph year (hence growing his ratings a little more than w/o playing time), then it can be worth it. Henry McKenzie was a 16 WE and has been a very good starting SG for my S. Arkansas team in Allen for the last few seasons.

It depends how many areas you practice and how much he plays. If he plays a lot early on and you're only focusing his practice minutes on a few categories than you will have no problem getting at least close to his caps.

If the guy gets a lot of playing time early, I would do it.  One of my best guys ever started with an 18 WE and has improved a ton with some room still to grow going into his senior year.  He was CPOY last year and pre-season first team all american going into this year.  He started from day 1 and improved his WE from 18 to 25 and it's now at 34.  So if he can start early, do it.