not sure if you will get a response from here. If you arrive without accommodation, you may be able to negotiate a deal on a holiday flat for the months of April, May & June & possible part of July.
Mainly the high tourist months are all of August and possible July and September, so it may not be that someone would rent to you for the inclusion of August, or if they did it would be for a much higher rate. It is different when you are renting somewhere for a year or longer.
Something to take on board, if you will have a car, check where you will be able to park it. some places have parking and other use the local parking.
good luck in your search, worth taking your time over something like that, i.e. not rushing, as you need to take on board all costs involved.