Best base coat for a house

well it depends.  Primer and Base coat are different things.  What color do you want the house?  Is it brick? stucko? wood?  that all depends.  Prime it in gray or white depending (gray makes the colors more dull, white makes them more vibrant)  then use a base coat near what you want, then detail over it.

FOR EXAMPLE

Mini art destroyed church. 

Primed in gray, base coated in a brick red from humbrol, and the windows in a light gray from humbrol. 

After that I used acrylics and oils to add shade and shadow to the bricks, windows, corners and whatnot.

the basecoat is just that, a base color to work ontop of

You may not need a primer.  What materials did you use to contruct your house?

I made it with some plastic sheets that you can buy at my lhs. I then covered it in squadron epoxy putty and smoothed it out to make it look like stucco.

I use either panzer grey, black or a dark brown when basecoating buildings...