Though TD Ameritrade now offer $0 commission, what are the recurring fees that are to be paid for using their services?

These fees are in line with the rest of the industry. TD may not be charging these fees to profit themselves, but rather due to exchange or regulatory requirements. You are unlikely to encounter most of the fees, such as Hard to Borrow fee which is for borrowing securities (e.g. to short), or Reg T extension/Forced Sell-out (as long as you don't use margin).

Another thing you should consider is the 30% withholding tax on US equities. You may want to consider Irish-domiciled ETFs which only have 15% withholding tax.