wifi in long thin rowhouse?

I just moved to a rowhouse that is long and thin and I'm sure many of you can relate. I get great wifi in one end, and like no wifi in the other. I know if I contact verizon there will be some kind of very expensive solution that will involve "renting" a piece of equipment from them indefinitely. Is this something I can hire a third party to fix, or does it kind of have to be Verizon because they are who did the original wiring? (I tried a Linksys extender- it does nothing.)