Combining two buildings into a single network via the Internet, how best to do it?

Question

Network administration

Good afternoon!
Actually the subject, I found some possible options on the Internet, but I would like to know how it would be better.
There are two buildings that need to be combined into a local network via the Internet, as I understand it, there are the following options:
1) renting a vpn server and letting traffic through it, but it seems that you will need to allocate separate computers for this and make a gateway out of it, just you need static ip-addresses for each building;
2) setting up your vpn server in one of the buildings and connecting the neighboring one to it, but gateways will still be needed.
A huge minus is that we only have an adsl connection with the provider, so the speed is not very good ..
You can extend the optics of course, but it's very expensive and the manual won't do it ..
What can you advise on this issue?

Answer 1

Combining two buildings into a single network

For what? What kind of traffic will go between them?
The transfer speed is meagre. Specifics of ADSL technology. Nothing good will come of it.
How many kilometers? Optical cable is not expensive.
Very expensive - how much? Or is it your assumption that it is expensive?