Does this hospitality SAAS idea already exist somewhere?

Yes, I did exactly that a few years back. A friend of mien and I launched a site with minimal functionality that was really just a landing page. We offered the opportunity to pre-buy a year's subscription to the service by allowing users to set their own pricing. Within the first 24 hours of the site going live, we had enough paying customers to validate the business and inform our iterative development cycle. Ultimately, we decided it wasn't a big enough business for either of us to get really excited about but it proves that it can be done. I also did that in my current business with a landing page that generated literally thousands of leads and hundreds of very qualified customers, which resulted in paid pilot contracts before the software was fully built. Build something that people actually *need* and you'd be surprised at what they're willing to do to get early access to it. Happy to talk about it in a call in more detail

Because the startup costs to get a lot of their customers actually set up on their platform are too high, so free trials for say, 14 days, are out of the question. For example, take a look at http://www.curalate.com/ which uses some really amazing technology to track a customer's brand imagery across (almost) the entire web. Naturally, most of these types of services are usually $300++/month, so again, it's all just about mitigating setup costs for the provider. Hope this helps :)

Most Software as a service vendors generally don't book annual deals except in highly specialized cases. Most customers prefer to be able to cancel/change anytime they choose. Also, deals done "offline" end up actually often being more trouble than they are worth to administrate especially for a $2988 ticket. Generally, companies don't view prepaying for SaaS products a year in advance as a "convenience" (to them) so if the debate is internal (not customer driven), I'd set this debate aside until it's requested by the customer. Most customers will request a discount to pre-pay annual service. Happy to talk this through with you in a call, to work through the specifics of your situation in more detail.

There is no valuation until you sell something. An idea or a company is only worth what its sales are. Once you have your initials sales, sales strategy and forecasting length (ie 9 months from first customer lead to close) then you have a formula for valuation. Valuation for start-ups is generally 3.5 x last years sales model should be the growth factor. When you are looking for investors, you will want to have atleast 9-18 months of SALES, not just pipeline and they will be looking at 5x revenue for a 3-5 year payback.

It's not foolish, but it's going to be extremely hard to pull it off. I would consider starting with a beta program so you can have some paid clients to pay for the company's expenses. After you have some traction, you can raise a seed round.