I would go as low as a 1.......on a transfer, maybe even a 2 year juco if I liked his stats enough. A 4 year player? no. I just recruited a 19 WE 4 year player this week, but I plan on RS him and then starting him 4 years. His cores are so much better than his peers. I think after 4 seasons and a RS, he'll max out to his full potential.
I think of WE a little bit like DUR, it doesn't affect your ability to play. For example, if you look at 2 recruits with equal overall ratings, the one with the lower WE may not improve as quickly, but he probably his higher cores.