To have any chance of turning a livable profit you would need to have a variety of hotspot locations available at
anchorages that are popular enough to be crowded regularly. You might think the overhead and setup cost would be low, but I'm not so sure that's the case.
My experience has been that sailors are
cheap folks (especially the ones at anchorages). Getting them to pay the amount of
money it'd take to make this business model
work probably is not viable.
Those who are tech savvy (or tech comfortable) will use their smart
phone as a wifi hotspot. Those who are non-tech savvy probably won't open their
laptop to look for an
internet connection, either because: they won't expect to find one, have other things to do or simply don't have a strong enough attachment to the internet to desire paying $15+ per day for it.
With that said, wifi hotspots at popular mooring/guest slip areas would be much more lucrative (I'm thinking locations like
Avalon,
Catalina Island). Usually if you moor at
Avalon you intend to spend some time in the city (not necessarily the case if you're at an anchorage). For this reason, local establishment advertisement services would be a much easier sell. Plus people at
anchorages often have the "sailing is free!" mentality. People at moorings are generally willing to spend money to make their experience more comfortable/enjoyable.
Additionally, it will be much cheaper to get a wifi hotspot going and maintained for a
mooring field located within an internet connected town/city since the infrastructure is already there. Off in the boonies at an anchorage? Not so much. If you are thinking of putting it in places that are so far from civilization they might require
satellite driven internet, I'd forget about any chances of profitability.
Honestly, this is not a business I'd be interested in getting into anywhere except the most densely moored/slipped areas (and even then, I'm skeptical the money coming in would cover the money going out, let alone living expenses).