It's tough. I'm not sure anyone is going to have an answer though that's going to strike you as too novel.
1) Are you sure you only have an enterprise product to sell? You sure no one in a business of 50 or fewer people need it?
2) Have you bought some credentials yet by giving your product away? We gave our product away to the first couple so we could do a couple things. Get feedback quickly instead of trying to wait a year or 2 to make a sale and then get feedback. Also then we had a couple credentials that we could mention to other clients and on our website to build credibility.
3) Have you done any freelancing? There's short term projects out there that could pay the company bills, they just take some finding.
If selling to large companies is a long sales cycle, then maybe selling to small ones can shorten it.
Selling major systems into the enterprise seems to have a long sales no matter what you do. It takes months to get everyone on board, and then get the (substantial) expenditures approved. It's not just the product cost, but the customer's costs to deploy the software.
Sales cycles are directly related to your product's cost. If you can sell something cheap, small, and low risk, you can cut the number of approvals, and shorten the cycle.
Small group or department level products have much shorter sales cycles and open the door for SMB sales. They make a lot of sense as part of a complete product portfolio, though you have to use different sales models to get them to market.
You many be able to charge for some of the preliminary work up front (business analysis, cost analysis, data conversion planning or integration feasability study, customizations, etc.). If they object, you can always agree to deduct the from the final purchase.