Been playing for about a week now, never caught a pikachu though 
Not that rare, I saw two yesterday. But they have a higher spawn rate in some events.
untill the next migration next thursday i have a nest at home, with 4 pikachu per hour 
It usually depends on where you play and in what weather. Here in my hometown, Pikachu is very rare, and when I find one it’s usually in rainy weather, only… or when there is an event with a special hat Pikachu, like for Christmas for example
Keep catching those Pikachu, you’ll might eventually get a Shiny 
With emphasis on electric types in May, I think he will be a little less rare.
You have a nest IN your home? Gosh, being Rural sucks.