A nostalgic adventurer returns to Greece to avoid the sale of his grand parents house in a week, but faces his coquettish parents who reject his lifestyle and blackmail him with the house, and his sandbox love as a badass broker who needs every cent during the financial crisis.

If you're asking for a personal opinion I don't find the house to be high enough stakes nor compelling enough motivation for a film but that's just me other people may disagree?

Well, thank you for your feedback, guys. I really appreciate that. It's hard to write a short and on point logline. I guess I have some work to do.
Actually, do you think it's a good motivation for a character to return to an old house to avoid the selling. I'm in the same situation, because I love the house of my grand parents and don't want it to get sold.
The house has a lot of feelings and emotions for me, because I spent almost every summer inside of it with my grandparents.
The character will also lose his memories of his grand parents, if the house will be sold.

I agree with Nir.

I thought it was fine up until the "sandbox lover", after that I just found myself confused.

I also think there would be a more succinct way to spell out the opening without having to mention the house twice.

I also don't think "Nostalgic" is a good character trait to use. Is it this nostalgia that causes him to want the house to remain in the family? I think it would make more sense if the house was in some way special. That would lead to a more interesting logline. Why does an adventurer need a house anyway?

Without knowing the true nature of the story I would go with something more like:
- After losing everything in the financial crisis, a rugged adventurer returns to Greece to prevent his greedy parents from selling his beloved Grandparent's home.