Castle Renovator

I'd recommend leaving this achievement until last as you'll naturally build up a surplus of building resources throughout the story and renting isn't unlocked until part way through anyway.

The quickest way to do this is to build a single foundation piece with a door wall piece attached, apply wood or stone to the door and then attach the rental sign, this will let you see the floor space requirements for the potential tenants and always build the the smallest requirement.

I built all my houses longways (1 square wide by however many the lowest tenant wanted long) then fill with the furniture requirements, if you're not hitting the value needed just put 3-4 mirrors on the wall and that should cover it.

Repeat however many times required for the achievement. The 4 'royal' tenants for the other achievements count towards the 30 so it's worth doing those first even though they're usually much larger houses assuming you're going for the full thousand