The final signing usually happens before a public notary or a registered conveyancing agent, depending on the country. The change of ownership is only complete when the register is updated, and this can take days or months.
The first thing to check is whether foreigners may own property there at all.
The costliest error remains taking legal advice from the other side. The agent is paid on completion, which is a different interest than protecting the buyer.
Ownership starts to make sense once the horizon is long enough. Entry and exit costs remain substantial, so a short stay seldom covers them. The standard advice points to a horizon of several years before buying beats renting.