All pre-paid minutes are used only when you call out to
someone. Receiving phone calls are FREE. So it's nice to have one to
be reached easily. 

For regular pre-paid sim cards, each costs NT 345 (around $10 USD).
No internet access. 

If you want the internet connection built in, it's NT 500 (around $18
USD) with 1GB max data transmission per month. 

But as long as it's a smart phone one carries, there are many free
wifi signals everywhere in Taipei, including on campus, the hotels,
some cafes, etc. 

If the students are hoping to bring their US cell phones to Taiwan,
make sure they check whether their phones are not locked by their
service carrier.... It happens sometimes that some US service carrier
lock the contract-bond phones (especially I-phones) provided for their
users.  So it's better to have the students check with their phone
carriers and to find out/unlock the phones before coming to Taiwan. 

Another related quick reminder- if the students are planning to use
their ATM cards to withdraw money while in Taiwan (easiest way to get
cash), you may also want to have the students check with their banks
on all related terms and inform them about their plans beforehand
too.