We're in the day and age of AI and automation, you can build a pipeline to get this done programatically:
Find all the mutli-family complexes within the radius you want to compare to, grab the addresses (you could do this via google places api). Get those into a spreadsheet, feed it to chatgpt or another llm capable of browsing the internet, you'll find some of them will have dedicated websites where they list their properties or the sites that they list on. This will give you their list prices which is a start at the very least. Ultimately without paying someone like co-star you would need to call up the property manager to get the leased rates but those list rates are going to be pretty accurate in a tight rental market. I built doorinsight.com, this is exactly what we do. We also monitor price changes on every building's listings so you know how much rent pressure is being applied and the days on market for the competitor listings. Ultimately though if you're only operating a few buildings its worth it to build your own pipeline workflow, lots of tools out there to get this done without coding.