Try using one of the real estate portals: https://www.zonaprop.com.ar/
(Buenos Aire's closest thing to Zillow) or https://www.properati.com.ar/
Realtors mostly totally suck in Buenos Aires. There used to be a few good ones but a TON of people have left the business. I find most to be totally flaky there.
If you're buying an apartment for short-term rental just make sure the building allows it as a lot of buildings have changed the HOA rules to forbid short-term rentals. So make sure when you're making an offer you specifically check the HOA rules and that short-term rentals are accepted. Even if they are, there is no guarantee that they won't change the rules after you buy it.
ROI is all across the board here. There is a TON of competition now as a ton of people are doing short-term rentals. If you're renting to a local your ROI can be really horrible. For example, I have several friends that are in amazing properties and they are paying really low rental rates. I recently went to a friend's place in Palermo Chico that had a penthouse apartment with huge outdoor space. Super nice. That property is probably worth $375,000 US or so and he was only paying $800 US a month! I guess his rent was $1,200 before COVID but his landlord lowered it as he was struggling. His landlord would rather have someone paying something than paying nothing. It will go back up but even at the higher rate that's not much at all.
One great thing is with the high blue dollar rate, you're income is in USD if you're renting on Airbnb and your expenses are all in pesos. For example, my HOA fees in US $ terms has actually gone down over the past few years as the US$ is much higher now. It's gone up with inflation but they can't raise it too much. It's 40,000 pesos a month for the HOA expenses but now that's only around $105 US whereas before it was much more.
Property taxes and ABL are relatively inexpensive compared to other countries. But as mentioned, you have a shit ton of competition these days. Plus I assume Argentina will go the way of many other countries and start adding on IVA and income taxes on Airbnb. My rental properties in Mexico the ROI has actually gone down this past year as Airbnb is charging 19% IVA and also they are charging all owners income tax on the income. I'm sure Argentina will do that as well soon.