Sure! For the better part of 2015 my job was to fly in to specific markets in the US and spend 2-4 days building a plan for a wireless ISP network that would be built a few months later. I'll summarize the process that I used, perhaps that will be helpful?

First I should explain that my experience is in fixed wireless networks[0] more than fiber.

First, I would spend some time on Google Earth looking for good neighborhoods to serve. A good neighborhood is typically a dense suburban development with low tree growth. Then I look for potential places to put the access points to serve the area - you really need line of site (no trees) to each home to provide good service. Water tanks, mountains/hills, office buildings and even residential homes make good access point locations. Often you can negotiate a rooftop lease with a place like that for a few hundred dollars a month (or even less). You can also use commercial cell phone towers, but they're more like 1-2k/month. You really want to be able to see a few hundred rooftops within 5-10 miles of your access point location to make it worthwhile.

Next you need to figure out how to get service to your access point location, like you mentioned. You really only need a few hundred mbps circuit to start though, a 1gbps circuit will last you up to a few hundred customers at least. Your first circuit shouldn't cost more than 2k to maybe 3.5k / month. The hard part is finding it in a place where you can then get it delivered to your access point location. Sometimes you get lucky and find an office building near a suburban neighborhood that already has a fiber demarc in the basement - that's a slam dunk. More often you have to lease space on an office building in the city, buy your fiber circuit there, and then use a high capacity wireless backhaul to relay the service to your access points. I would usually just drive around the main roadways looking for the orange stickered fiber whips to see where the fiber lines run, then call the company to get pricing. (can't find a photo at the moment, I'll keep looking.)

Then, you just start building and signing people up. Lot's of people make the mistake of trying to go cheap on the customer install, many WISPs start by trying to install their customers with in-home radios rather than putting them on the roof. That doesn't work. Regardless of the type of equipment you use, you have to put a good radio on the roof with a reasonably high gain directional antenna pointing to your tower. The other common early pitfall is to try to use regular WiFi devices for your network. WiFi is designed to work well in buildings / office parks, not so much outside and long-ish distances. Ubiquiti equipment is a good start and very cheap, although there are better ones.

The hardest part about signing up customers is paying for their equipment up front. You're looking at 250-350$ per customer installation (including amortizing infrastructure build) if you're in an area where the incumbent is really bad you can sometimes charge some of that to the customer. The ROI isn't too bad even if you eat that cost - less than a year - but it can be hard when you're starting out.

The next hard part is jumping over the scaling humps. You'll need a staffed support center and NOC before you're fully able to afford it, for example. Disclaimer - this is what I'm working on know, providing a variety of the backend services that these WISPs usually need / benefit from but can't afford to build on their own.

[0] https://en.wikipedia.org/wiki/Wireless_Internet_service_prov...