A seawall isn't going to stop the water from reaching your house. It will (maybe) protect the soil from being washed away from the banking, but if the water comes up 4 feet, its going to come up 4 feet whether your wall is there or not. Also, most of the time a "wall" will end up failing and the soil will get washed away from behind it and you will be wasting your money. It may take 15 years for this to happen, but it frequently does happen, unless you have NO waves at all. If you have any scouring tidal flow or wave action then you will be better off using a contractor that uses rocks to protect the bank. These are large and are skillfully knit together to resist waves and hold your bank. This is expensive.
My opinion about waterside homes is that they should be for rich people that can absorb the financial loss of losing their property without using public funds for subsidised flood insurance and flood prevention. If losing this house to the elements would significantly set you back then you should sell it and live in the woods.