do you know others are already doing this and they actually PAY THE SHOP OWNER for putting wifi there? They generate ads from the wifi and the revenue are being shared. Example, starbucks free wifi.

not sure how much they paying them. It depends on the ads revenue. You can change your business model to something like this.

These company already have established system to install wifi in hotels and other big chain restaurants. And they already have advertisers that will pay them. Your idea is good but you have to compete with them. I am sure there are still market out there.