Most mutual fund companies, including both Vanguard and TRowe Price, will accept smaller monthly contributions if there is an agreement to on a certain day of the month make an electronic transfer from a bank account to the IRA. Of course, if the bank and mutual fund company are notified before the monthly date, and cash is needed for something else, a monthly contribution can be skipped or they can be stopped. Vanguard will assess a quarterly fee of $2.50 if an index fund account contains less than $10000.
$25 monthly contributions the fund companies don't sneer at if they are accompanied by a signature in the documents to open the account stating that this amount is to be transferred monthly.
So he should get started!
Best wishes, Chris