Your best bet will be to set up a savings account tat you dont have easy access to and when ready to buy transfer the money and buy from a reputable company like apmex.com or jmbullion.
Why? Just go to a local Gold and Silver store with your cash, and walk away with the precious metal.
You want someone else automatically withdrawing as much money as they want from your bank account to buy gold coins....That sounds like it would end well.
You can check this site....but there is minimum investment....
Is there a site that will automatically take funds from my bank BUT SEND ME THE PHYSICAL METAL once I have deposited enough funds to cover the desired coin? For a minimal fee on shipping etc...? Thanks for the help!