What kind of ants are these?
I cannot tell from the pictures, but pray they aren't Pharaoh or Argentine ants, as they are the absolute worst to get rid of once they "take hold". Those two don't have a single colony - like say carpenter ants - that one could kill and be rid of. They have many, many "sub-colonies", all with multiple queens, that just keep on going like the Energizer Bunny. They also make nests just about anywhere, a crack in the sidewalk, void in the wall, under stones, in leaves, under doormats, behind siding, bottoms of planters.....basically anywhere.
If you find one nest, there's going to be dozens more all over the place, and you'll have your exterminator on speed dial. You'll have to make sure you kill all colonies inside the house, a tall order if they've been around for a while, then have the perimeter of the house treated to keep them from coming back inside, otherwise you'll just be rinsing and repeating yourself with extermination fees. All it takes is one queen to get back in the house for them to be all over the place in no time.