The nastier the planet, the more important it is to have adequate shelter for the colonists. Troops are tougher, and don't really care (at least they aren't allowed to complain). The initial boatload will set up adequate housing for the starting population. The Environment, or Construction, industry is used to build new housing for additional colonists, whether they immigrate from one of the Imperial planets or are born in the colony.
The important figure for monitoring the living conditions of the colony is the Effective Habitability, which is found on the Economic Report. Effective Habitability is defined as the ratio of population (with troops counting half) to available housing. The initial base will be established with an Effective Habitability of 80, and it normally will be maintained at a level above 75 if adequate resources are devoted to construction. As the population grows, more housing will have to be built, or the effective habitability of the colony will fall, from overcrowding and inadequate facilities. Usually, 10 to 20 percent of the work force is allocated to construction of new houses, but a colony that is rapidly gaining people will have to devote more to provide for the immigrants. The number of housing units available in the colony is also printed in the Economic Report. If there are more houses than people, Effective Habitability will be 100. In this case, you will be able to safely increase immigration.
If the effective habitability falls below 70, the life support system for the colony may fail from overloading. The first symptom of this will be the failure of the agricultural systems, and a probable loss of population.
Note that the colony will normally not permit immigration to drive the Effective Habitability below 75. Intrinsic population growth, on the other hand, has no such restraints.