If he’s in the US - and that’s an assumption, I know, since he hasn’t said - prepaid plans aren’t all that smartphone friendly. I gather it’s better in Europe.
Verzion’s prepaid smartphone plans are exactly like their postpaid plans. It’s a $45 / month. Since prepaid never includes a phone subsidy, it makes more sense to go with a regular plan, unless you can get a smartphone under $60.
AT&T has a $30 / month plan, with which data runs $5 / 100 MB / 30 days. Speaking from experience, 100 MB is actually a lot of data if you’re careful not to do anything but email and similar things unless you’re using Wifi, but you have to be disciplined about it.
T-mobile has $3 / month for 30 minutes air time + $0.10 / minute after, which is great for a very infrequent phone user like myself, but the data terms are unfriendly. It’s $5 for a daily pass and $10 for a weekly pass. If you use mobile data frequently, you might as well go with their $40 / month prepaid plan. Which is better than $50 regular plan, since t-mobile doesn’t do phone subsidies for those.