Man who built ISP instead of paying Comcast $50K expands to hundreds of homes

As the other commenters have pointed out, a possibility is simply to "resell" transit from other providers. However, on the Internet all peering networks are somewhat equal and it's entirely possible to extend the "other end" over time to establish dedicated peering with other networks, so that for example traffic from your network to Youtube doesn't have to go through (paid-for) 3rd parties.

There's good chances there are Internet eXchange Points around where you live where for a small maintenance fee anyone can come and place their router and cables to interconnect with others.

So the likely steps are:

1) Find a transit provider, that will serve your trafic to any other network, and where to connect with this provider 2) (Optional) If you don't have the necessary infrastructure, find another provider to get from your last-mile network to your transit provider 3) (Optional) Find other networks to peer with so that you can significantly reduce your transit bill and provide better routes (therefore better service)

Some non-profit ISPs take the problem from the other side, and build a core network without necessarily owning any last-mile infrastructure, which is leased from other operators (opérateurs de collecte) with whom they interconnect at some datacenter/IXP. The most famous example of that in France is FDN.fr which has been operating since early 90s. That approach is more cost-effective in high-density area where the local infrastructure is already quite good, and construction jobs to lay new cables is very costly, but will still set you back 10-30€/month/line.