Nightclub/lounge financing is undoubtedly one of the trickiest to secure. You could be at for a while or have a one of a kind concept and partner up with someone overnight. The key as you probably know is to go in with a few silent partners to share the risk. Having been involved with a few, i would confirm that a well run club would return the $5.5M in 3-4 years or less. I have seen business plans for nightclubs in Puerto Rico, NYC etc and one of the things they all lack is a coherent marketing strategy and extensive operational experience. Startup costs are on ofe the biggest issue as a huge amount of capital is required for startup and most of it turns into sunk costs in the form of property improvements and furniture, fixtures etc. A good entertainment setup in one of the lower end NYC clubs alone is approx $400,000. Costs and Margins are another story....and perhaps a lecture in itself

All details aside, i do think that the cost of $5.5 million sounds excessive, despit have a restaurant component to it (unless you are buying very expensive RE). I have seen a few trendy spots in NYC and Miami cost $2.2-4 million. Maybe as per your lounge/business concept its justified. I would advise you to do a detailed market study and contact some owners of existing successful nightclubs or restaurants. I think you will have the best luck with them (Do keep marketing ideas to yourself). Other than that i do not think that you will even close to $5.5 M business loan or equity investment from a traditional lender or as private equity from someone who is not in the business.
Best of luck!