When I was house farming I had around 400 blue houses.
Just to throw out some #s, that 770,000 you would pay for 100 white houses will buy 427 blue houses@1800 each.
Blue houses earn $150 every 8 hours, but to compare them to the white houses, lets say you check them every 12 hours, and lets round it down a little to 400 houses.
so checking every 12 hours (to compare to the white houses) that would be 60,000 every 12 hors or 120,000 a day. 3 times as much as you would make with the white houses.
Yes, 400 houses is a lot to tap, you could always cut that down to around 133 blue houses(150 per tap) to have the equal income of 100 white houses (200 per tap) every 12 hours, and only have to spend about 240,000 initially to make the same income. And if there are days you can get in 3 taps(every 8 hours) instead of 2 (every 12) that's extra money.
And as fuffazzoni said, they won't be a permanent fixture in your town, when you get higher level, you will find you won't need the farm any more to sustain your town.