That's actually incredibly illegal. You're not allowed by the FCC to intentionally put noise out that interferes with other people's equipment.
Also, ALL wifi stuff is considered 'low power' because of it's power levels. It's not talking about 50mw cards in your home router vs the 200mw cards put up on the towers. It's talking about devices which compared to traditional radio equipment is 'low power'. Generally speaking, this is stuff which has a transmission radius of approximately 10-15 miles without amps, etc.
Finally, commercial wireless carriers are a way of providing an alternate means of internet connectivity in places which are notoriously hard to get connected such as dense urban areas (Because you need to get permission from the city to use the right of ways), or rural areas which could cost thousands to run copper or fiber miles out just to get $20-100/month.
And, yes, there are grants for that stuff. But generally speaking it's not very feasible for small companies to do as the government is very strict on how you manage it. It can actually cost a small ISP a large chunk of the grant itself just proving to the government that they're spending the grant the way it was meant to be.