Effectiveness of WiFi extenders...

Yeah, you can put an extender/repeater where it gets a strong signal in the second home, and it should cover the rest of the house with a stronger signal. A cheap repeater with just one radio will cut the bandwidth in half, though. More expensive ones with two radios won't have that problem. Or you could replace the existing router with a better one with longer range.

I use them in my house and have mixed results. I'm using TP Link AV500, which extends WiFi and also creates a "wired" connection over your home's electrical wires. The wireless connection is pretty good at being extended; only complaint is that my phone struggles to jump from one access point to another. I can't really blame this on extender though because it is my phone that is trying to stay on the weak signal as long as possible. (tried several apps, none work well for me with this)

I do love the "wired" connection. I'm getting around 30-40 mbps speeds over wires on the opposite side of the house from the router. I'd recommend this unit for this feature alone. (sorry, this doesn't help your situation, but I thought I'd share for others that might be interested)

stick one of these in your attic

LINK