At the point someone gives you $500,000, they are subject to a gift tax (so they would be paying). Once you receive the money though, it would be yours free and clear so you would only be subject to the capital gains (the 500K would be part of the basis).

NOTE: I'm not an accountant, so you should really check with one and give them your detailed specifics if you are going to go forward.

My assumption from your question is that a company would buy this for their managers to use. If that is the case, building a freemium version would not guarantee that the company would actually turn around and purchase the product (or premium version) in the future. If you have pilots with companies that are well established names, that should be enough to start trying to get new customers and generate revenue. The surest way to know if your product is good enough is to ask people to pay for it. The fact that you could use some money at this point, only reinforces the decision.

Two other quick points to add to the above suggestions. Questions regarding what made them buy the product or service in the first place will give you a lot of insight as well. For example: What made you choose our product over others available? You can send the question open ended to a small percentage of your 10,000 customers and provide a multiple choice option for the remainder (or once you get some insight from the open ended responses). Secondly, understanding what customers were doing as a workaround before purchasing your product will give insight into how to best target future customers, so include questions regarding this as well.

A lot depends on what you are selling. If it's somewhat of a low risk proposition, going with a small company may not be as much of an issue. If you're looking at a higher risk/exposure product or service, a large company will want to make sure you're well capitalized, will back up your product or service, can scale and provide quick response when there are problems. Think of it this way; You're an executive at a large company and you have to meet deadlines and deliver or management is going to be on your back. Do you risk going with a small provider who may have all the issues discussed above or do you go with a large provider with deep pockets and more extensive resources? The best approach for a small company is to really show expertise and quality in your product or service over and above your competitors. You can try to play bigger than you are, but being upfront and really micro-focusing on solving their problems is usually the best approach. The more comfortable they get with your ability to address their problem better than anyone else, the easier the other objections will fall away.

I'd have to concur with Steve Mason's answer above. You can sit around and try to brainstorm big problems, but you are limited to what you personally have been exposed to and can relate to. Getting involved with contracting or consulting will give you insight into many different environments that you normally would not have known existed. Try to determine what industry you truly have interest in and start there. Get involved with everything and anything you can within that industry (e.g. associations, developer groups, contracting, etc). As you become more and more involved with that industry, you'll start to understand the nuances of the participants and the mindset. From there, you can start to really focus your efforts on uncovering the best opportunities to address.