But seriously, the informed commentaries (such as those of the estimable LQ above in this thread) that I've seen seem to indicate that a generic router attached to the SL gear would support an affordable ethernet cable (say Category 6) of 100 meters, which should include the gentle bending required to fit the cable to your indoor gear, plus, if needed, the burial of the cable in some cheap PVC pipe to reach the neighbors house, and then their installation.
I did such an installation to my office in the redwoods, and at 100 mt (the published maximum spec) there was no signal slowdown for DSL. Goofy people everywhere use WiFi unnecessarily, but if it were appropriate in your situation, I don't know if it would effect performance.
There are Microwave systems for a few hundred bucks that require line of sight and many have a range of a mile or so that might interface with SL - some of them are considered 'plug and play'.
I've always thought this kind of facility sharing was a great idea, with the right partners...