I always recommend buying your own modem. I purchased this modem a couple of years ago and it's been great:

https://www.amazon.com/TP-Link-Cable-Download-680Mbps-Certified/dp/B01CVOLKKQ/

Netgear makes a similar modem that would work well too. You will likely be paying for internet for several years and renting a modem throughout that time will add up.