I knew that if my web host went down, I would lose sales. The web host (like most of them) offers a 99.9% uptime guarantee, but a $5 to $10 refund just doesn't match up to losing hundreds of dollars in sales.
I could get a dedicated host, and that would cost a lot more money every month. Even with a dedicated host, if the hosting provider came under a denial of service attack or lost their upstream connection to the internet I would still be down.
I finally solved the problem with a company called DNS Made Easy (not an affiliate link).
First, I had to have at least two hosting providers, with each one offering a dedicated IP address option (it might work without a dedicated IP, but I haven't tried it). I set purchased the home user membership at DNS made easy, and also purchased two system monitoring options for a total of $24.85 per year.
I set up my DNS made easy account to hit each of my hosting providers every few minutes. If either host is not responding, they will direct all of my traffic to the other responding host. If both are responding, the traffic will be balanced between them.
I now have one domain being hosted out of two different data centers. Just to check, I have had a program loading my own website every fifteen minutes for over two months, and I have had 100% uptime, even though both of my hosting providers have gone down during that time.