Starting with a rental is still the reversible decision in an unfamiliar country. Districts change character between seasons, and noise only becomes obvious with time. A year of renting is far cheaper than correcting a purchase in the wrong area.
Ownership starts to make sense when the time horizon is long. The costs of buying property in tavira and selling are substantial, so a short stay almost never pays them back. The standard advice suggests a horizon of several years before ownership pays off.
Borrowing locally shifts the calculation considerably. Non-residents often face higher down payments and shorter terms than domestic buyers. Where local lending is unavailable, the purchase means an all-cash transaction, which alters what else that capital could do.
Renting preserves freedom of movement. A shift in circumstances, personal circumstances or a regulatory change can be absorbed with a notice period, rather than a sale that takes months. In markets where prices move slowly, the ability to leave quickly is worth a great deal.
Buying brings advantages a rental never will: protection from rent increases, the right to alter the property in sagres, and an asset you actually hold. In some countries, ownership may also strengthen a residence application. The practical answer for most people amounts to renting while you learn the market and buying afterwards.