I'm not willing to take the risk. Some salespeople have presented me to some pianos and proudly said:
"This one has over 100 years! You should take a look!"
There is no excuse for terrible sound, other than bad tuning. Wurlitzer's bargain line had a thick soundboard that wouldn't let the sound out. I have one I paid $50 for. It sounds a lot brighter with the top taken off, but I can't read the music that way. I keep it in my trailer I camp out the summer in, to exercise my fingers. The top line Wurlitzer studio down at the Spring**** Methodist church sounds great, Duke Ellington played Wurlitzer grands some, there is a picture.
But globalization has meant the production engineers have been busy making sure your new product will all fall apart at the same time. Just like cars.
Real pianos are not like cars, they are worn out by 1. hours of use (tens of thousands) 2. too much humidity/rain 3. vermin damage. Unfortunately you live in a country where 2 & 3 are pretty prevalent.
The brands I quoted above are real pianos: before the names were bought by mega-corporations and slapped on modern insta-****. Unfortunately I don't know the Mercosur market to recommend what is good and what is **** down there. We had our carefully engineered to fall apart pianos here, I'll mention W*****y, K*****l my home county built piano. My sister-in-law bought some lion logo brand in the late eighties, selling my Mother's Everett. The movement is sticking up twenty years later in the garage- which IMHO the old Baldwin's in unheated leaky churches do not do. I played a fifties baldwin Hamilton all summer in a 10 member country church. No issues. I've played century old beater uprights in Sunday School, that had mostly a missing keytop problem. There were also **** uprights built in the twenties, my grandmother had a Cincinatti, which looked like a Baldwin but sounded like **** and fell apart in the thirties.
As far as the one year store guarentee on tuning, if they reseat or fix in the loose pin if one droops too fast, fine. I suspect what the store will do is give you two free tunings to get it past the warranty. Loose pins are not that common, but they do happen. Idiots that don't know how to hold a wrench straight while tuning, are one cause. Try that on a lugnut sometime with the " free" wrench that comes with the car, then watch your car with a flat tire get towed to the tire shop with a boogered nut.
Strings don't wear out unless overtightened in tuning. Strings do snap occasionally, especially after long gaps in interval, but the treble ones are easlily replaced. i've done it on my Sohmer, with industrial music wire no less, not even something special from the piano store. That one sounds better than the looped over string on my 41 Steinway, that goes faintly "boink". Matching broken bass strings (overwound) in a 2nd world country may be a real problem, unless the manufacturer is still in business. Forturnately bass strings don't sag pitch much and don't need tightened as much as treble, either.
To emphasize, dirt and rust on the insides are not problems. Mouse damage and mold on the felt are.
Stores concentrate on good furniture, most buyers won't do the tests above, and most won't practice more than 100 hours in the life of the product, either.
New products that hold up here are Yamaha Kawai & Steinway. I don't like the sound of the former consoles, although their concert grands sound okay. Petrov, Fazoli, Bechstein, Bosendorfer, I've never seen any of those in person.
Best luck shopping