I use betterment and vanguard. Betterment allows me to set up a monthly contribution and it allocates that to a variety of domestic and internatiknal index fund

I use betterment and vanguard. Betterment allows me to set up a monthly contribution and it allocates that to a variety of domestic and internatiknal index funds as well as bonds. They also rebalance automatically. With vanguard you have to have a minimum of $3000 for most funds. I think once you have 3k in a given fund I think it is easy to make auto deposits with vanguard too.