In my experience of being part of the acquiree, you can get acquired for a gross earnings multiple of between 30 and 40. So as long you're only spending 2.5m per year to get your 5 mil run rate then yep, find the right acquirer and you can get that 100m valuation but there's a lot luck involved.
you can also incorporate before applying (if you're serious about the idea). Use services like LegalZoom, they cost around $300-$600.
In the event that you do get into YC, or raise 5-6 figures of seed money, you can always go to a lawyer and reissue stock certs, articles of incorporation, etc.
i suspect it's the free WiFis that require you to comply with their terms and conditions. They probably catch the traffic and inject text ads into the HTML, which arguably is quite clever and malicious.
Beats the "here's 2+2" type problems.