What is the best online broker for a Roth IRA if I have a lump sum to open with but not $ to put in regularly?

I am going back to school soon and won’t have extra money to contribute for the next couple years, but would like to at least start the account so it can grow. Most info I’ve read says to compare annual fees and trading fees, and obviously I don’t want to pay an annual fee if I’m not putting new money in to offset it and also don’t think I’ll do a lot of trading right now.