The absence of slippage and re-qoutes will also help to have a profitable income but it does not mean that the profit is guaranteed. There's no such business that have a guaranteed profits.

There are some platforms that guarantee no slippage they charge you an extra 3 pips in every trade, so it can mount up. You may be best just sticking with a bit of slippage. It's part of the risk inherent in the markets, and I'd be very wary of any broker that guarantees no slippage. If they're not covering themselves, it's almost certainly a scam.