Your IP will change if it's dynamic. Ask for a static IP or at the VERY LEAST a sticky IP with a decent DHCP lease. Some ISPs do care about high traffic sites. That's enough said about that, just give 'em a call. Your bandwidth is most likely throttled, if you need more call your ISP. Ask for someone in the tech department, not in sales... don't waste their time acting smart- just tell them, in English, what it is you're wanting.
You'll want a domain name, right? You need to change the A records to point to your machines IP, that's a pita if it keeps changing every day. You're also going to want decent name servers so don't pick a fly-by-night registrar.
If your power goes out during a storm, your site goes down. If that doesn't bother you- good, because there aren't many alternatives.
Keeping your machine on 24/7 processing traffic means your electric bill will go up, not a joke. Disks don't spin on wishes. Awwwwwwwwwww, I wish my electricity bill was zero :rolleyes:
Configuring Apache can be hours of trouble. Security updates are required if you don't want someone sitting on your box. Windows in general is impossibly hard to secure, the mandatory access controls are this never ending mess. But as an administrator you should probably have that all figured out eh?
You want SSL? Well unless your visitors trust you or someone in a chain of CAs leading up to a known CA- prepare to fork over some money to a big-name CA to sign your cert. $100 for a year. But a hobbyist doesn't need this- plus you're smart, find a central authentication system you trust (like Open ID, they pay for a signed cert).
All in all you're talking about spending $10 to $20 USD to get set up ($10 domain registration, $0-10 sticky IP), plus ~10 hours to get an open port for the world, plus ~10 hours configuring your services properly, plus ~20 hours if you have ADHD.