Licensing is a complex topic that varies considerably by location. By state, and then by county or municipality.
Overhead can be relatively low, depending on what you have in mind. You need some basic infrastructure- ice machine, coolers, CO2 systems, etc. Insurance is a bit different for a bar than other businesses, obviously, but not too bad. Inventory is a low cost compared to your cash flow, as is labor since pretty much everyone will be minimum wage plus tips. Maintenance isn't too bad.
Basically a well-run bar is a license to print money. You sell drinks for several multiples of your cost of goods.
Most bars I knew of that had trouble had it due to owners that didn't know what they were doing, at all, in terms of business, or more commonly had a drinking/substance problem.