First the business question, how do you find enterprise clients? Do a PPC on Adword? Cold call? How do you introduce yourself to companies you are looking to build an enterprise application for with the goal of scaling and monetizing it, making clear I hold the IP?
any ideas on how to find a company willing to work with you on a study case for free by building an enterprise application for them at much reduced cost? The finding part would be the hardest but this would be also hard to convince them for free programming service, I will hold the right to my future commercial software?
The real question is do you know who could benefit from your software, and how? I don't mean in general terms like "every company needs an accounting system" but rather very specific terms like "because of new regulations taking effect in country X, any foreign corporation with over 100 employees doing business there and using hazardous chemicals must have an on-line database with current Material Safety Data Sheets".
When you have that kind of very specific, targeted knowledge of who needs your software and why then you are in an excellent position to contact them directly and discuss your offering. In cases like this general ads and PPC are a waste of time and money.
On the other hand if you do not have good information on who might benefit from your service and why, then discovering that information should be your top priority.
From my own experience, you usually get most of your enterprise clients among companies people you've worked with in a way or another, and people you already know from elsewhere. Basically this is networking, networking, networking and networking again. So yes, actually LinkedIn counts. It may even counts a whole lot.
Cold phoning may work, but it's extremely tough and unrewarding because you have to get prepared to call 2000 times, get screamed at 100 times, ignored 1800 times, find interested people 100 times, and get finally 5 meetings, of which you'll maybe obtain 1 or 2 customers in the end. So you really want to have the nerves to go over that, not everybody does, especially not the nerd programmer type :)
AdWords may work. However in the past few years it quickly degraded from a sure way to get customers when spending 500-1000 euros/month to something you need to carefully attend for to get some bang for the buck. Be prepared to study your keywords and statistics, make many tries and spend some money on it before getting results.
Speaking of it, website quality and landing pages are of absolutely tremendous importance to web ad conversion. Don't ever forget that.