pd1jap

Hello BB aka @pd1jap
I can’t help with current guys, but I do know Buenos Aires well from having spent a year there. 
Assuming you can speak Spanish well, it’s easy to meet guys (working and non-working). Argentines do set great store on being in-shape (tho this may be less important to a rentboy) and being well-dressed in public.
You can see a selection of working guys on various sites (eg soytuyo) but be aware the photos may be old. There are numerous ‘telos’, hotels with decent facilities that rent rooms by the hour, in Recoleta.
There is a lot of info on Argentina in various threads on this site. Please be aware of the high level of street crime and robbery, and be savvy about carrying/wearing valuables and using public transport.
You state you will be ‘staying in Palermo’ but you will need to be much more specific in making arrangements. There are several neighbourhoods named Palermo. There is Palermo Chico, which is a district of rich families generally. And there are Palermo Soho and Palermo Hollywood which are middle-class areas (some fancy parts and some newly-gentrified) with various restaurants and many boutiques.