HouseCanary is a leading data feed and is $150k/year. MLS offers a limited feed for around $1,500/month. You can scrape Zillow and use a captcha handler tool for $30/month.

There are distinct differences in these approaches. Zillow’s data lags 3-4 weeks while HouseCanary’s is about as real time as you can get. MLS can be weird and is typically market-specific. With all of that said, you can’t just login to a website and have this available. There is legwork required.