In my opinion, you could, but it's not worth $50. If your school has a service, great, you can have him send it there for free. If not, just drop him an e-mail every few months and/or try to do a little something with him next summer, and then get the letter junior year.
$50 bucks is a lot for a letter that two years down the line you may not even want to use anymore (who knows what will come along?).