The biggest one is taking legal advice from the other side. The agent is paid on completion, which is not the same as looking after your interests. Separate legal representation costs a fraction of what is at stake and is money well spent.
Putting your name to untranslated contracts ranks close behind. A certified translation is inexpensive compared with the sum being committed. Verbal assurances will not help once a dispute starts — the document governs.
Purchasing off-plan on trust has wrecked a great many buyers. Ahead of a deposit, review what the company has already delivered, the construction licences, and whether payments are held buy property in cikcilli escrow. Late deliveries are common even in good markets; unfinished projects are less common but much more damaging.
Forgetting about resale is a quieter mistake. A home bought abroad has to be sold or passed on at some point, and the next buyer matters. A home that only appeals to foreign buyers is harder to move when sentiment turns.
Finally, a lot of buyers underestimate the ongoing obligations. Annual declarations can be required even buy property in skiathos years with no rental income, and overlooked notices lead to charges nobody warns you about. Putting in place a local tax adviser from the first year heads off most of these problems.