What you need to know:
Once you get past the lamers-following-scripts "customer service" reps, it's surprisingly easy to get a static IP, even a static IPv6 address, from major ISPs. I haven't done this with Comcast, but Centurylink was easy. You may have to buy "business class" service. Comcast will want you to run their router so they can have yet another "Xfinity" wireless access point leeching off your bandwith to them.
You have to pay extra for DNS, which always seems odd to me, like it's a scam for domain name registrars to make extra money.
Your machine will be probed mercilessly. Nearly 100% of SMTP traffic is spam. Way more than half of HTTP traffic is bots. Put ssh on something other than port 22, put a honey pot or tar pit (endlessh is good) on port 22. Occasionally you'll get DDoSed for no reason you can figure out.