If all of your users will be using either FileMaker Pro or FileMaker Go to access the database, then you do not need IWP--which can only be done with FileMaker Pro or FileMaker Server Advanced. You can just use FileMaker Server.
Some people choose to pay a hosting company to host their database with FileMaker Server Advanced for them if they need to make it accessible to users with Web Browsers.
A quick look on Google show a few hosting companies that look like a good compromise. Are there any limitations on a hosted solution that your aware of? A recommendations ?
Thanks for the response!
You'd need to talk to them and ask questions specific to your needs.
If your solution sends out email, you may want to see what they have in terms of an SMTP server, for example.
If you've never used IWP, create the IWP solution and test it on your own machine first before spending any money on hosting services. Compared to using filemaker clients, IWP can feel like tap dancing in a phone booth--some really cool moves are possible, but only if you can keep from colliding with the limits of what a web browser can do with an IWP FileMaker database.