Urban point-to-point link / meshnet

I have some friends living fairly close to each other, and it would be fun to set up a full meshnet. However, for the time being I just want to get a bit familiar with radio technology and the hardware available, so I was thinking of doing a simple point-to-point interface between two fixed positions, to first do some quality assurance testing.

I looked a bit around, and found some WiFi routers touting up to 2km (and even 5km) range, but I figure that would be greatly reduced in an urban environment. I also looked at AM/FM radio, and it seems there are some options there as well, however the lower end options claimed no more than 1km range, falling a bit short. (And also seemed like it required much more technical know-how.)

The distance we want to cover is about 1.2km, but lets say 1.5 to be safe. It's pretty flat between us, not ups and downs, just a slight constant decline the one direction. But there are lots of build in between, and no direct line of sight. We live in each our apartment, and have little (legal) access to rooftops - although it could possibly be made some deals with the landlords. (Especially if this is something we could pitch as beneficial for the neighborhood, some sort of pilot program.)

Encrypted communication is a must, but it wouldn't require very high bandwidth to begin with. But having to get certified and licensed is out of the question. Also, our budget isn't massive, but we are prepared to make a small investment.

So, what are we left with, if any? Do you see any possibility of setting up a direct link between the locations? What technology and hardware is available? Or are we simply delusional?