Connecting networks for two buildings
I want to interconnect the LAN of two houses. They are just across each other on the same street.
With WLAN I had a quite high network latency.
Are there faster, inexpensive alternatives?
So you want to have one Internet connection in one house and share that connection with another house.
If I read your question correctly, it sounds like you have tried this and have some latency problems.
I assume you have a wireless router in the home (A) with the Internet connection and wireless devices in the other house (B). And I assume the distance between the two houses is perhaps 250 feet or less.
The latency could be caused by interference and low signal strength causing failed data transmissions requiring many retries for each successful data transmission.
First, make sure the specs on the router indicate it should work for the distance you are dealing with (probably not the issue, but check anyway). Perhaps a better router will solve all your problems.
Try re-positioning the router in (A) and a device in (B) to see if the latency can be improved. For example, try putting the router (A) and a device (B) near the front of each house.
Things like Aluminum siding, or a metal shed between the router and the devices in the other house will significantly reduce signal strength.
A "Repeater" or "Range-Extender" could significantly help and are fairly inexpensive. Try to find a place to put one outside (you only need to run power to it). Could be under a car-port, under the roof-overhang, or garage, or a shed, or under an awning. If all else fails, consider putting it in a small bird-house hanging from a tree or poll or above a fence (remember you need to run power to it). The weather in your area may affect what you can do with this.
You could first, as a trial, place the range-extender out in the open at various places around your property to get an idea if it will work, and to find the best place to put it before you make it a "permanent" installation. In extreme cases, you may need to have a range-extender on both properties.