The very first thing we did (mostly my wife) was to call Comcast, give them the specific address, and have them verify the place had high speed Internet.

For those that passed that test (a relatively low percentage did since we were looking to live in a relatively rural area) the next thing we did was contact the relevant real-estate agent. This part was tricky and often annoying. We cut through everything they had to say and said that, if they wanted to potentially move forward, they had to do something for us. They had to get permission from the current owner and run an Internet speed test.

This was a PITA, but most of the time they did it. And most of the time, Comcast's data was accurate about whether service was available.

The place we ended up buying is about 10 miles outside of Olympia Washington. Our street is one of the very few in the area that has high speed comcast.

Having said that, we also got a starlink dishy right away and we use that as backup, because while most of the time our Internet is really excellent, speed is great, etc, it has a lot of small outages, so it's worth having a highly reliable but much less fast backup.